JP2756084B2 - Flux-cored wire for gas shielded arc welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an gas flux cored wire for shielded arc welding filled with titania-based flux, in particular, it has excellent weldability and low temperature toughness in all position welding, heat treatment after welding (welding Heat treatment for the purpose of softening the heat-affected zone, improving the ductility and notch toughness of the weld zone, and reducing the residual welding stress:
The present invention relates to a flux-cored wire for gas shielded arc welding applicable to specifications (hereinafter referred to as PWHT).

[0002]

2. Description of the Related Art In recent years, the development of energy resources tends to be polar and deep sea, and there is a strong demand for the development of steel materials and welding materials having excellent low-temperature toughness. However, titania-based flux-cored wire for gas shielded arc welding has excellent welding workability in all positions of welding and is highly efficient, but the amount of oxygen in the deposited metal is high and the (Hereinafter referred to as Weld)
Application up to about 0 ° C. was common.

[0003] On the other hand, the basic wire has a relatively low amount of oxygen in the deposited metal, and in both the As Weld specification and the PWHT specification, good low-temperature toughness can be obtained, but the workability in all-position welding is poor. Practically, there are many problems because they are much inferior to those based on flux cored wires.

Further, in recent years, as shown in Japanese Patent No. 1407581, in a titania-based flux-cored wire, a low temperature specification of -60 to -80 ° C. is used due to a synergistic effect of alloy components such as Ti, B, Mg, and Ni. Although technology has been developed that makes it possible to apply the technology to AS,
It is a technology mainly based on the WELD specification, and it has been difficult to sufficiently apply it to the PWHT specification such as stress relief annealing. In addition, this conventional technique does not sufficiently meet the demand for high toughness such as COD characteristics.

Further, in order to improve low temperature toughness including COD characteristics, a technique in which the amount of fluoride in the flux is increased (Japanese Patent Publication No. 5-45360) has been proposed. When used, in addition to the large amount of welding fume and spatter generated, CaF ₂
When the addition amount of BaF ₂ or the like is large, the basicity of the slag increases, and the weldability in the upright position is extremely deteriorated, so that it is difficult to apply to all position welding.

[0006]

As described above, conventionally, there has been no technique capable of realizing both excellent workability in all-position welding and good low-temperature toughness in AS WELD specification and PWHT specification.

[0007] Conventionally, Nb yield in the weld metal
There are findings that the amounts of V and P have an adverse effect on toughness after stress relief annealing, but most of those findings relate to submerged arc welding and MIG welding where the amount of oxygen in the deposited metal is relatively low. And its application temperature was at most about -40 ° C.

[0008] The weld metal formed by the conventional titania-based flux-cored wire has a high Nb and V content,
It was generally known that embrittlement was caused by PWHT. However, in the region of a weld metal having a relatively high oxygen content, such as a weld metal made of a titania-based flux-cored wire, the allowable range of the content of P, Nb, V, etc. that can achieve good low-temperature toughness is as follows. It is not clear, and further, a low temperature range of -60 to -80 ° C has not been sufficiently studied.

The present invention has been made in view of the above problems, and is required for an LPG ship, an LNG ship, and construction of an offshore structure in an ice sea area, for example, -60 to -8.
A titania-based alloy that has excellent toughness values such as Charpy impact value and COD value in AS WELD and PWHT at 0 ° C. level, and at the same time, good workability in all position welding.
And to provide a gas shielded arc welding flux cored wire.

[0010]

Means for Solving the Problems] This flux-cored wire for gas shielded arc welding according to the invention, the welding gas to obtain leave and weld metal Charpy impact value was excellent at -60 ° C. In the heat treatment condition after welding in the flux-cored wire for shielded arc welding, a percentage of the total wire weight, 3 to 9% in terms of TiO ₂ values titanium oxide containing TiO _2, the Nb 0.0001 to 0.0120%
Not less than 0.02% V as an impurity
(Including 0%) , and (Nb + 0.5 × V) is set to 0.1.
It is characterized in that it is restricted to 0001 to 0.0150% and P as an impurity is restricted to 0.02% or less.

In addition, one or both of the steel sheath and the filling flux are: Si: 0.1 to 1.2%, Mn: 1.0 to 3.
0%, B; 0.001 to 0.025%, and metal fluoride (in terms of F amount): 0.01 to 0.30%.

[0012] Further, the steel outer skin may contain P as an impurity.
Is preferably restricted to not more than 0.010% based on the total weight of the steel shell.

[0013]

The present inventor has conducted various studies to improve the toughness of the weld metal formed by the titania-based flux-cored wire. When reheated to a temperature range of about ° C, fine carbides and nitrides were precipitated, and it was found that the toughness was extremely deteriorated.
The appropriate ranges of b and V amounts were clarified.

In a conventional titania-based flux cored wire, the oxygen content of the weld metal is generally 700 to 900.
Since it is as high as about ppm, a sufficient crystal grain refining effect cannot be obtained even when a complex addition of Ti and B is performed, and good low-temperature toughness cannot be obtained in a temperature range of −30 ° C. or lower. It is also known that the addition of Mg to the flux lowers the oxygen content of the deposited metal to some extent and improves the low-temperature toughness in AS WELD specifications, but it is still insufficient when PWHT is performed. Depending on the conditions such as temperature and time of the PWHT, the demand for impact performance of about 0 ° C. is often not met. In order to make this possible, conventionally, it has been responded by reducing the oxygen content of the weld metal with a basic flux cored wire. As described above, the titania-based flux-cored wire has not been able to sufficiently meet the requirements of the PWHT specification.

The inventors of the present invention have conducted intensive studies on the weld metal formed of the titania-based flux-cored wire to improve its low-temperature toughness. Even in this case, by limiting the amounts of Nb, V and P in the wire to a predetermined range, the AS WELD specification and P
It has been found that good low-temperature toughness can be obtained up to a low temperature range in any of the WHT specifications. The present invention has been completed from such a viewpoint. That is, in the present invention, the optimum amounts of Nb, V, and P in the weld metal are defined based on the wire components.

[0016]

Next, the results of various experiments that led to the completion of the present invention will be described. In order to improve the low temperature toughness of the weld metal of the titania-based flux-cored wire, the flux composition was variously examined by welding tests. The welding conditions are as follows. Test Wire wire diameter: 1.2 mm cross-section was performed welding tests using the wire having a composition shown in 15% welding condition shown in Table 1 below: FIG. 5 (b) as shown in a seamed wire flux filling rate below . (Charpy impact test) ... according to JIS Z3111. Polarity: DCEP (DC reverse polarity (wire (+))) Welding current: 280 A Welding voltage: 27 V Test steel sheet: BS4360 Gr50D Shielding gas: 80% Ar-20% CO ₂ mixed gas Others: Welded according to JIS Z3313 . (COD test) ... according to BS5762-1979. Polarity: DCEP Welding current: 180 to 280 A Welding voltage: appropriate Test steel sheet: BS4360 Gr50D, thickness 40 mm,
60 ° X groove Shield gas: 80% Ar-20% CO ₂ mixed gas.

[0017]

[Table 1] Table 1 (Part 1) ┌───┬────┬─────┬────┬───┬────┬──┬──┐ │ │ Made of steel Outer skin Including TiO ₂ │ │ │ │ │ │ │ │ P content │ Titanium oxide │ Nb │ V │ Nb + 0.5 V │ Si │ Mn │ │ No.│ │ TiO ₂ │ │ │ │ │ │ │ │ │ (%) │Converted value │ │ │ │ │ │ │ ├─┬─┼────┼─────┼────┼───┼────┼──┼──┤ │ │ 1│ 0.008 │ 4 │0.00011 │0.010 │ 0.0051 │0.8 │1.3 │ │ │ 2│ 0.004 │ 7 │0.0110 │0.001 │ 0.0115 │0.9 │2.0 │ │Real│ 3 │ 0.006 │8 │0.006 │0.015 │ 0.0135 │0.4 │1.8 │ │ │ 4│ 0.009 │ 7 │0.0013 │0.0010│ 0.0018 │0.7 │2.6 │ │Application│ 5│ 0.008 │ 3 │0.0002 │0.010 │ 0.0052 │0.4 │2.0 │ │ │ 6│ 0.004 │ 6 │ 0.001 │0.0010│ 0.0015 │0.5 │1.9 │ │Example│ 7│ 0.006 │ 9 │0.005 │0.005 │ 0.0075 0.6 │2.2 │ │ │ 8│ 0.009 │ 7 │0.0005 │0.010 │ 0.0055 │0.5 │1.9 │ │ │ 9│ 0.008 │ 6 │0.0004 │0.002 │ 0.0014 │0.4 │2.2 │ │ │10│ 0.004 │ 7 │0.010 │ 0.003 │ 0.0115 │ 0.5 │ 2.3 │ ├─┼─┼────┼─────┼────┼───┼────┼──┼──┤ │ Ratio │ 11 │ 0.006 │ 6 │ 0.00005 │ 0.0015 │ 0.0008 │ 0.3 │ 1.2 │ │ │ 12 │ 0.003 │ 3 │ 0.013 │ 0.0001 │ 0.0135 │ 1.1 │ 1.4 │ │ Comparison │ 13 │ 0.003 │ 4 │ 0.0010 │ 0.021 │ 0.0115 │ 0.8 │ 2.4 │ │ │14│ 0.003 │ 5 │0.009 │0.014 │ 0.0160 │0.5 │2.0 │ │Example│15│ 0.005 │7 │0.0018 │0.010 │ 0.0068 │0.3 │1.5 │ │ │16│ 0.012 │ 4 │0.004 │0.005 │ 0.0065 │0.6 │1.7 │ └─┴─┴────┴─────┴────┴───┴────┴──┴──┘ Table 1 (Part 2) ┌── ─┬──────┬──────┬───┬──── ────────┐ │ │ B │ Metal fluorides │ P │ Detergents other than TiO ₂ │ │ │ (B amount converted value) │ (F amount converted value) │ ├──┬──┬ ───┬──┤ │ No.│ │ │ │ │SiO ₂ │ZrO ₂ │Al ₂ O ₃ │FeO │ ├─┬─┼──────┼──────┼───┼ ──┼──┼───┼──┤ │ │ 1│ 0.023 │ 0.08 │0.011 │0.3 │0.1 │-│-│ │ │ │ 2│ 0.010 │ 0.15 │0.010 │1.2 │0.6 │ 0.1 │-│ │ Actual│ 3│ 0.002 │ 0.09 │0.015 │0.4 │0.2 │-│0.1 │ │ │ 4│ 0.015 │ 0.20 │0.018 │0.2 │0.3 │-│0.1 │ │Application│ 5│ 0.005 │ 0.02 │0.011 │0.4 │- │ 0.1 │-│ │ │ 6│ 0.006 │ 0.05 │0.010 │0.5 │-│-│-│ │Example│ 7│ 0.007 │ 0.10 │0.015 │0.3 │-│-│0.1 │ │ │ 8│ 0.008 │ 0.15 │ 0.015 │0.4 │0.1 │ 0.1 │-│ │ │ 9│ 0.005 │ 0.03 │0.010 │0.5 │-│-│-│ │ │10│ 0.006 │ 0.04 │0.011 │0.3 │-│-│-│ │ │Ratio│ 11│ 0.004 │ 0.05 │0.008 │0.2 │0.1 │-│-│ │ │12│ 0.004 │ 0.23 │0.012 │0.4 │0.4 │-│-│ │Comparison │13│ 0.010 │0.05 │0.010 │0.6 │0.3 │- │-│ │ │14│ 0.015 │ 0.04 │0.008 │0.1 │0.2 │-│-│ │Example│15│ 0.020 │ 0.11 │ 0.024 │0.3 │0.2 │ 0.1 │-│ │ │16│ 0.004 │ 0.08 │ 0.021 │ 0.2 │0.2 │ 0.2 │-│ └─┴─┴──────┴──────┴───┴──┴──┴───┴──┘ Table 1 (Part 3) │ │ No.│ Ni │ Mg │ Fe │ Ti │ Other │ ├─┬─┼── ─┼───┼───┼───┼───────┤ │ │ 1│ 1.2 │ 0.5 │ 4.0 │-│-│ │ │ 2│ 0.1 │-│- -│-│ │ Real │ 3 │ 2.6 │-│ 6.0 │-│-│ │ │ 4 │-│ 0.4 │ 4.5 │-│-│ │ │ 5 │ 1.4 │-│ 4.0 │-│-│ │ 6│ 1.4 │-│ 4.0 │-│-│ │ │ 7│-│-│ 4.1 │ 0.01 │-│ │ │ 8│-│-│ 3.8 │-│ Mo = 0.5 │ │ Example │ 9│-│- │ 4.0 │-│ Cr = 0.2 │ │ │ 10│-│-│ 3.8 │-│ Al = 0.1 │ │ │ │ │ │ │ │ │ Zr = 0.1 │ ├─┼─┼───┼───┼─ │ │ Ratio │ 11 │ 3.6 │ 0.7 │ 3.0 │-│-│ │ │ 12 │ 1.1 │ 0.5 │ 5.0 │-│-│ │ Comparison │ 13 │ 0.5 │ 0.2 │ 2.3 │-│-│ │ │14│-│ 0.1 │ 6.0 │ 0.01 │-│ │Example │15│-│-│ 1.5 │-│-│ │ │16│ 2.3 │ 0.3 │ 2.8 │-│ -│ └─┴─┴───┴───┴───┴───┴───────┘

In Table 1, underlines indicate components outside the range specified in the present invention. The results of the Charpy impact test and the COD test of the weld metal are shown in FIGS.

FIG. 1 shows the amount of Nb in the wire (% by weight) on the horizontal axis.
And the vertical axis represents the impact value (v
FIG. 9 is a graph showing the relationship between the Nb content in the wire and the impact value, taking E-60 ° C., J). In the figure, open circles indicate 620 ° C
, The impact value of the sample subjected to stress relief annealing by heating for 10 hours, and the solid circle represents the impact value of the sample as welded (AS WELD). Similarly, FIG.
FIG. 3 is a graph showing the relationship between the amount of Nb + 0.5 V in the wire and the impact value, and FIG. 4 is a graph showing the relationship between the amount of P in the wire and the impact value. FIG.

From these figures, in order to improve the low-temperature toughness of the titania-based flux-cored wire, it is important to regulate not only the P amount but also the Nb and V component amounts appropriately.

As described above, in order to improve the low-temperature toughness of the titania-based flux-cored wire, it is necessary to suppress P, to reduce Nb,
Regulation of V and (Nb + 0.5 × V) is essential, and any of these factors reduces the effect. That is, by controlling the above factors, AS WE
In any of the LD specifications and the PWHT specifications such as SR, a titania-based flux-cored wire having a remarkably improved low-temperature toughness can be obtained.

Next, the reasons for adding the components and the reasons for limiting the composition of the titania-based flux-cored wire of the present invention completed based on the above experimental results will be described. (Reason for component limitation) TiO ₂ (titanium oxide) TiO ₂ is a main component of the titania-based filling flux, and is an essential component as a slag forming agent and as an arc stabilizer. %. TiO ₂ has excellent encapsulation and peeling properties not found in other slag forming agents, and also has excellent properties as an arc stabilizer. If the titanium oxide content is less than 3% in terms of TiO ₂ , good bead appearance and bead shape cannot be obtained, and spatter increases. In particular, the bead dripping drastically in the vertical position and the upward position, and a good weld cannot be obtained. On the other hand, if the titanium oxide content exceeds 9%, the slag generation amount and the slag viscosity become excessive, slag entrainment occurs, and welding workability is reduced.

The TiO ₂ source includes natural and synthetic rutile, reduced illuminite, lucoxin, illuminite, and oxides such as potassium titanate.

[0024] Nb, V and (Nb + 0.5 × V) N b influences the crystal structure and mechanical properties of the weld metal in trace amounts, if an appropriate amount, in the form of primarily carbides and nitrides in the crystal structure It is uniformly dispersed and acts as a nucleus for the generation of fine acicular ferrite, and also has the effect of increasing the toughness and strength of the weld metal in order to fix the impurity nitrogen. It is extremely effective for suppressing a decrease in toughness. In particular, Nb is extremely effective for suppressing a decrease in the toughness of the raw material part of AS WELD. As can be seen from FIG.
In order to obtain the effect of improving toughness by adding Nb, it is necessary to contain Nb in an amount of 0.0001% or more based on the total weight of the wire.

On the other hand, Nb is 0.0120% and V is 0.0
If it is contained in the wire in excess of 200%, carbides and nitrides are significantly formed in the reheated region of the weld metal, hardening and deteriorating toughness. When the stress relief annealing (SR) treatment is performed, carbide precipitation of Nb and V spreads over the entire crystal structure, as in the case of the reheat region of AS WELD, and the toughness is significantly deteriorated. For this reason, when performing SR processing, as can be seen from FIG.
It is desirable to regulate as follows.

There is a difference between Nb and V in the contribution rate to the toughness degradation, and the parameter (Nb + 0.5 × V) is a factor that shows the tendency of the toughness degradation. (Nb +
0.5 × V) needs to be 0.0001 to 0.0150%. The upper limit and the lower limit of (Nb + 0.5 × V) are based on the above-described limitation in the case of adding Nb and V alone.

Further, Nb, V and (Nb + ／ × V)
Is more preferably Nb: 0.0001 to 0.01.
00%, V: 0 to 0.015%, Nb + ／ × V:
0.000010 to 0.0100%. This is because high notch toughness is obtained and high fracture toughness (for example, AS
COD value (at-10) in WELD or PWHT specifications
° C) ≥ 0.25 mm).

P (phosphorus) P is an element having a strong effect on low-temperature toughness, and as its content increases, toughness deteriorates. As shown in FIG. 4, the brittle P compound precipitates at the crystal grain boundaries by the stress relief annealing (SR) treatment, so that P deteriorates toughness. In the range where the P content is 0.015% or less based on the total weight ratio of the wire, almost the same impact value is obtained irrespective of the P content, but it tends to decrease slightly at 0.015%. 0.02
At 0%, it is greatly deteriorated. Further, the P content has the same effect on the COD value as the Charby impact value. Therefore, P
Must be suppressed to 0.020% or less, and preferably regulated to 0.015% or less.

Further, there is a difference in yield between the amount of P yielded from the steel shell into the weld metal and the amount of P yielded from the flux into the weld metal. That is, since P is more likely to be present in the weld metal from the steel shell, it is necessary to suppress the P content of the steel shell to 0.010% or less for the above reason.

Si (Silicon) Si improves the bead appearance and bead shape, and maintains good welding workability. Furthermore, Si has the effect of promoting the deoxidation of the deposited metal and increasing the yield by the deposited metal. The effect of these Si additions is 0.1
% Is effective when added. However, if the Si content exceeds 1.2%, the yield to the deposited metal becomes excessive, the crystal grains become coarse, and the notch toughness decreases.

Mn (Manganese) Like Mn, Mn also improves bead appearance and bead shape and welding workability by adding an appropriate amount, and promotes deoxidation of a deposited metal. In addition, a part of Mn yields in the deposited metal to enhance the quenchability, refine the original portion of the crystal structure,
It has the effect of increasing the toughness and the strength. In order to obtain these effects, it is necessary to add Mn by 1.0% or more. However, when the amount of Mn added exceeds 3.0%, the yield to the deposited metal becomes excessive, the strength is increased more than necessary, and cracks are likely to occur.

As the Mn and Si sources of the flux, electrolytic Mn, Fe-Mn, Fe-Si, Si-Mn alloy and the like are used.

B (boron) By adding B in an amount of 0.001% or more, an excellent effect of improving notch toughness can be obtained. However, when the amount of B is 0.0
If it exceeds 25%, the toughness improving effect is sharply reduced, and the tensile strength is excessively increased by quenching and hardening, so that cracks are easily generated. In addition, B can be added as an alloy such as Fe-B or B oxide. In the case of a B alloy or a B oxide, a value converted into a B amount is added in a range of 0.001 to 0.025%.
The B oxide is reduced to B during welding, and performs the same function.

Metal Fluoride Metal fluoride can enhance the arc stability and also has the effect of increasing the low-temperature toughness of the deposited metal by the dehydrogenation effect. These effects are expressed in terms of the amount of F relative to the total weight of the wire. Effectively exhibited by adding 0.01% or more. However, the amount of metal fluoride was 0.30 in terms of F amount.
%, The amount of spatter and fume increases, the welding workability decreases, the fluidity of the slag becomes excessive, and the bead shape deteriorates. For metal fluorides, Na,
Fluorides of alkali metals and alkaline earth metals such as K, Li, Mg, Ca and the like are generally used.

[0035] is as the component composition than is required in other filled flux used in the present invention, it is also possible to add other alloying elements such as in a range capable of satisfying the other requirements described above. For example, if 0.2 to 0.8% of Mg is added,
The oxygen content in the weld metal can be considerably reduced without greatly deteriorating the welding workability, and the low-temperature toughness at a level of -60 ° C can be further increased.

If 1 to 4% of Ni is added, the low-temperature toughness can be increased without impairing the workability.

Furthermore, 0.1 to 1.1% of Mo or 0.2%
If 3.5% of Cr is added, the high-temperature strength can be increased. Furthermore, as a deoxidizing agent or a denitrifying agent, or in order to prevent dripping of a molten pool in vertical welding, Al or Z
r may be added at a ratio of 0.5% or less based on the total weight of the wire.

Further, in order to improve the weather resistance, a small amount of N
i, Cr or Cu can also be added. Furthermore,
As the arc stabilizer, oxides or carbonates of alkali metals such as K, Na and Li, compounds of rare earth elements such as Ce and La, iron powder and the like can also be added.

The titania-based flux having the above-described composition is filled in a steel sheath in accordance with a conventional method to produce a flux-cored wire. A cold rolled steel or a hot rolled steel having good deep drawability from the viewpoint of filling workability may be used as the steel outer cover. The filling rate of the flux is not particularly limited, but is most preferably in the range of 10 to 30% based on the total weight of the wire.

FIG. 5 shows the cross-sectional shape of the wire.
There are various shapes shown in (a), (b), (c), and (d), but it is not limited to these.

The wire shown in FIG. 5 (a) fills the inside of the strip-shaped steel sheath M with the flux F, and
Bend into a tube so that the edges of
Thereafter, the wire is drawn to a predetermined diameter. The butt end face of this wire is flat, but FIG. 5B shows the butt end face curved. FIG. 5C shows a butt end portion bent in an L-shape to widen the butt end surface. FIG. 5 (d) shows a seamless steel shell M filled with flux F.

In the case of a wire having the shape shown in FIG. 5D, the surface of the wire may be plated with Al or Cu. In this case, the plating amount is suitably 0.05 to 0.30%. The wire diameter is also arbitrary, but can be determined from 1.2, 1.4, 1.6, 2.0, 2.4 and 3.2 mm depending on the application.

Further, when performing gas shield arc welding using this wire, oxidizing,
Neutral and reducing gases can be applied. As a general shielding gas, CO ₂ , Ar, CO ₂ , O ₂ and He gas or a mixed gas of two or more thereof can be used.

Next, the results of comparing the toughness and welding workability of the deposited metal between the wire of the example of the present invention and the wire of the comparative example will be described.

A test wire having a cross-sectional shape shown in FIG. 5B was prepared so as to have the composition shown in Table 1. Then, using each test wire, the Charbie impact test described above and C
Welding under the conditions of the OD test, AS Weld and S
The toughness and welding workability of the weld metal after R were investigated.

The test results are shown in Table 2 below.

[0047]

[Table 2]

In particular, Examples 8 and 9 also had good high-temperature strength. In the tenth embodiment, dripping of the molten pool in a vertical position is particularly small.

As shown in Table 2, in Examples of the present invention, the toughness after AS WELD and SR, particularly,
The low-temperature toughness of about -60 ° C required for LPG and LNG ships or marine structures is good, and the welding work for all-position welding is also excellent. On the other hand, the wire of the comparative example is AS
If the weld metal after WELD or SR treatment has low toughness,
Or welding workability was low.

[0050]

As described above, according to the present invention,
Since the amount of titanium oxide in the wire, the amount of Nb and V, and the relationship between both are specified appropriately, and the amount of P in the wire is specified, the toughness of the obtained weld metal, especially the impact value at low temperature, is extremely low. It is excellent and also has excellent welding workability. For this reason, the present invention is extremely useful in the field of gas shielded arc welding of LPG ships and LNG ships used at extremely low temperatures, and offshore structures in ice waters.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the Nb content (logarithmic representation) in a wire and the impact value of a weld metal.

FIG. 2 is a view showing a relationship between a V amount (logarithmic display) in a wire and an impact value of a weld metal.

FIG. 3 is a diagram showing the relationship between the amount of Nb + 0.5 V in the wire (logarithmic display) and the impact value of the weld metal.

FIG. 4 is a diagram showing the relationship between the amount of P in a wire and the impact value of a weld metal.

FIG. 5 is a diagram illustrating an example of a cross-sectional shape of a flux-cored wire.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Hosoi 100-1 Urakawachi, Miyama-ji, Fujisawa-shi, Kanagawa Prefecture Kobe Steel, Ltd. Fujisawa Works (56) References JP-A-4-300092 (JP, A) JP-A-5-77086 (JP, A) JP-A-4-224094 (JP, A) JP-A-2-192894 (JP, A) JP 2-15320 (JP, B2) JP-B 63-16239 (JP JP, B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) B23K 35/368 B23K 35/30

Claims (3)

(57) [Claims] (1) As-welded and after-weld heat treatment in a state of -6
In 0 gas shielded arc welding flux cored wire for Charpy impact value to obtain a good weld metal in ° C., as a percentage of the total wire weight, the titanium oxide containing TiO ₂ in terms of TiO ₂ value 3 to 9% , Nb in an amount of 0.0001 to 0.0120%, V as an impurity is controlled to 0.02% or less (including 0%) , and (Nb + 0.5 × V) is adjusted to 0.0001 to 0.01 %.
A flux-cored wire for gas shielded arc welding, wherein the flux is regulated to 50% and P as an impurity is regulated to 0.02% or less. 2. One or both of the steel shell and the filling flux, in total and in proportion to the total weight of the wire,
i: 0.1 to 1.2%, Mn: 1.0 to 3.0%,
B: 0.001 to 0.025%, (by F equivalence) metal fluorides: for gas shielded arc welding according to claim 1, characterized in that it contains 0.01 to 0.30% Flux-cored wire. 3. The steel outer cover contains P as an impurity,
The flux-cored wire for gas shielded arc welding according to claim 1 or 2, wherein the flux is regulated to not more than 0.010% based on the total weight of the steel sheath.