JP2001219291A - Weld zone of ferritic stainless steel and welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a weld zone in which the huge growth of the crystal structure of weld metal which is a problem in welding for ferritic stainless steel is suppressed, and cracks at the time of welding and cracks caused by the repeated application of stress can be prevented. SOLUTION: A weld zone having a composition consisting of by weight, C of 0.05% or less, Si of 2.0% or less, Mn of 2.0% or less, Cr of 15 to 25%, Ti and (or) Al of 0.05 to 0.5% and N of 0.05 to 0.3%, in which the content of P is controlled to 0.03% or less and S to 0.01% or less, and the balance substantial Fe, and in which the crystal grain size of weld metal is made fine by allowing the ones of the nitrides or oxides of Ti and Al and also with the grain size of 0.5 μm or more to exist at a density of 250 pieces/mm2 or more is obtained. The alloy composition of the weld zone may be the one containing Mo and (or) W of 5.0% or less, or may be the one containing one or more kinds among Nb of 1.0% or less, Zr of 0.1% or less and B of 0.1% or less in place of the above, or together with the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in welding technology for ferritic stainless steel, and more particularly, to a welded portion in which weld cracks are prevented and a welding method for providing the same.

[0002]

2. Description of the Related Art When welding a metal base material using a filler metal, it is common sense that the alloy composition of the filler material matches that of the base metal as much as possible. It is well known that the same type of steel wire is used for the welding of ferritic stainless steel, but that the weld obtained by welding has a very large crystal grain size and is susceptible to weld cracking. Even if welding cracks can be avoided, the weld is liable to crack when stress is applied repeatedly, resulting in low fatigue properties. In order to cope with this problem, it is necessary to make the crystal grains of the welded part as fine as possible, and the following measures have been proposed so far.

[0003] One of the methods is to use a nitride. There is a method in which Ti is added to a welding wire to thereby disperse TiN in a weld metal to reduce the size of crystal grains (Japanese Patent Laid-Open No. 5-138394). This welding wire is welded using a shielding gas such as 80% Ar-20% CO ₂ .

[0004] Another technique is to use an appropriate amount of A on the welding wire.
It is intended to add l and Mg in a complex manner to achieve equiaxed crystallization and fine graining due to the coexistence of these elements (JP-A-9-22).
No. 5680). The welding is performed by TIG, MIG, or the like.

[0005] These known techniques, however, are still not fully satisfactory, and further improvements have been sought.
The applicant has developed and has already proposed a welding method for achieving equiaxed crystallization and grain refinement of a weld metal using a welding wire to which Al, Ti and N are added in combination, and realizing an improvement in ductility and toughness. (Japanese Patent Application No. 11-255926). As a result of subsequent research, it was possible to obtain a weld metal having a finer crystal structure by controlling nitrides and oxides present in the weld metal.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problem in welding of ferritic stainless steel, that is, to suppress the crystal structure of the weld metal from growing enormously, and to repeatedly apply cracks and stress during welding. The purpose of the present invention is to realize a welded portion that can prevent cracks caused by cracks. It is also an object of the present invention to provide a welding method for providing such a weld.

[0007]

The welded part of ferritic stainless steel of the present invention is a welded part obtained by welding a ferritic stainless steel base material using a ferritic stainless steel welding wire. As alloy compositions, C: 0.05% or less, Si: 2.0% or less, Mn: 2.0% or less, Cr: 15 to 25%, and Ti and / or Al: 0.05-0.5% and N: 0.05-0.3%, P: 0.03%
Hereinafter, S: 0.01% or less, and the balance is substantially Fe
And 250 or more nitrides or oxides of Ti and Al having a particle diameter of 0.5 μm or more /
It is a welded part in which the crystal grain size of the weld metal is reduced by being present at a density of mm ² or more.

The method for welding ferritic stainless steel of the present invention is a method for welding a ferritic stainless steel base material, wherein a ferrite stainless steel wire having any of the following alloy compositions is used as a welding wire. I) C: 0.05% or less, Si: 2.0% or less, Mn:
2.0% or less, Cr: 15 to 25%, and Ti and / or Al: 0.05 to 0.5%, N: 0.0
5 to 0.3%, with the balance being substantially Fe II) In addition to (I) above, Mo and / or W:
III) In addition to the above (I) or (II), Nb: 0.5%
% Or less, Zr: 0.1% or less, and B: 0.1% or less. Contains one, two or three types as a shielding gas.
Welding is carried out using the following gas), a) Ar + (0 to 20%) O ₂ b) Ar + (0 to 20%) O ₂ + (0 to 50%) CO ₂ c) Ar + (0 -20%) O ₂ + (0-50%) CO ₂ +
(0 to 100%) He A nitride or an oxide of Ti and Al having a particle diameter of 0.5 μm or more is present at a rate of 250 pieces / mm ² or more in the weld metal portion, so that This is a welding method for obtaining a weld having a fine crystal grain size.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The alloy composition of the welded portion is determined by adding Mo and / or W: 5.
It may contain 0% or less. In addition to the basic alloy composition, Nb: 0.5% or less, Zr: 0.
1% or less and B: 0.1% or less of 1, 2, or 3
It may contain seeds. Further, it may contain both of the additional elements belonging to these two groups.

The reason why the alloy composition of the weld is determined as described above is as follows.

C: 0.05% or less C imparts strength to the weld metal, so that C must be present to some extent. However, if the content is increased, martensite is generated to increase the hardness of the weld metal and to easily cause weld cracking. Therefore, the content should not exceed 0.05%.

Si: 2.0% or less Si is not only useful as a deoxidizing agent at the time of smelting steel, but also a useful element for resistance to weld cracking. However, the addition of a large amount impairs the toughness of the weld metal.
Preferably, the addition is not more than 1.5%.

Mn: 2.0% or less Mn also serves as a deoxidizing agent. However, an excessively large amount is not preferable because corrosion resistance, particularly oxidation resistance, is lowered. The amount of addition is 2.0% or less, preferably 1.0% or less.

Cr: 15 to 25% Cr is an important component for increasing the strength of the weld metal and ensuring corrosion resistance. In order to obtain a sufficient effect, addition of 15% or more is required. However, even if a large amount is added, the effect is saturated and the cost is increased. Therefore, the upper limit is set to 25%.

Ti and / or Al: 0.05-
0.5% Ti and Al produce nitrides and oxides and act to refine the crystal grains of the weld metal. It is desirable to use both. In order to secure the density of the large nitrides and oxides described above, it is necessary to add one or both (in the case of a combined use, a total amount of 0.05% or more). From the viewpoint of arc stabilization and formation of a bead having an excellent shape, these elements are harmful.
Choose an addition amount that does not exceed.

N: 0.05-0.3% In order to allow a large-sized nitride to be present in the weld metal at a sufficient density, N must be present in an amount of 0.05% or more. on the other hand,
Since the presence of a large amount may impair the integrity of the weld metal, 0.3% is set as the upper limit of the content.

P: 0.03% or less, S: 0.01% or less Since both P and S are impurities that easily cause weld cracking and lower the toughness, the content should be as low as possible. The above values are acceptable limits.

The effects of the elements added arbitrarily and the reasons for limiting the composition range are as follows.

Mo and / or W: 5.0% or less Since Mo and W both increase the high-temperature strength, it is preferable to add an appropriate amount. If added in a large amount, the impact value and the corrosion resistance are reduced, so the addition of up to 0.5% is appropriate.

Nb: 1.0% or less, Zr: 0.1% or less, B: 0.1% or less 1 type, 2 types or 3 types Nb, Zr and B refine the crystal grains of the weld metal. To act. Since the presence of a large amount is detrimental to the stabilization of the arc and the bead shape, Nb is 1.0%, Z
r and B were set with 0.1% as the upper limit.

A nitride or oxide of Ti and Al having a particle size of 0.5 μm or more is present at a density of 250 or more / mm ² , such as a nitride or oxide distributed in a weld metal. A relatively large inclusion having a particle diameter of 0.5 μm or more is useful for refining the crystal of the weld metal, and its density is 25%.
It is an important opportunity of the present invention to find that effective miniaturization is realized only when the number is 0 / mm ² or more.
The close relationship between the number of inclusions and the crystal grain size is apparent in the examples described later.

The method for welding ferritic stainless steel according to the present invention may have a different form from the above-described method.
The welding method uses a ferrite stainless steel wire having any of the following alloy compositions as a welding wire. IV) C: 0.05% or less, Si: 2.0% or less, Mn:
2.0% or less, Cr: 15 to 25%, and Ti and / or Al: 0.05 to 0.5%;
0.03% or less, S: 0.01% or less, the balance being substantially Fe V) In addition to the above (IV), Mo and / or W:
5.0% or less VI) In addition to the above (IV) or (V), Nb: 0.5%
Hereinafter, Zr: 0.1% or less and B: 0.1% or less 1
Species or two or more types are contained. As a shielding gas, one of the following compositions (volume%,
Welding is carried out using the same gas as in the following), d) Ar + (1 to 10)% O ₂ + (2 to 30)% N ₂ e) Ar + (1 to 10)% O ₂ + (1 to 20) )% CO ₂ +
_{(2~30)% N 2 f)} Ar + (1~10)% O 2 + (1~20)% CO 2 +
To (0~100)% He + (2~30 )% N 2 weld metal, a nitride of Ti and Al or oxides in a 250 more than a particle diameter of 0.5μm to pieces / mm ² or more at a rate This is a welding method for obtaining a welded part in which the crystal grain size of the weld metal is made fine by making it exist.

The above group of welding wires (IV),
(V) and (VI) can also be used in combination with the shielding gas groups (d), (e) and (f), and such embodiments are also included in the welding method of the present invention.

The above (I) to (III) defined as the alloy composition of the welding wire contains N in its component,
This produces nitrides (primarily TiN) during solidification of the weld metal. At the same time, an oxide (mainly Al ₂ O ₃ ) is also generated, and both act together to help refine the crystal grains, as described above. The generation of nitride is also realized by adding an appropriate amount of N ₂ gas to the shielding gas. The methods adopted are the shielding gas compositions (d) to (f). In this case, since it is not essential that the N component is present in the welding wire, a welding wire having the above-mentioned wire alloy compositions (IV) to (VI) may be used. This corresponds to this.

Even if the shielding gas composition contains N ₂ gas, the presence of the N component in the welding wire does not matter at all, so the welding wire compositions (I) to (III) and the shielding gas compositions (d) to (D) Of course, f) may be combined. Such a case is the third mode of the welding method.

The composition of the shielding gas used in the present invention is as follows:
There is no difference in principle from that used for ordinary gas shielded arc welding. For example, the O ₂ component in the shielding gas helps stabilize the arc, and this effect is obtained in the presence of 1% or more, while exceeding 10% causes oxidation of the weld metal, which is unfavorable. A range of 10% is given. CO ₂ acts to stabilize the arc, and this effect is also observed when the addition is about 1%. However, if it exceeds 20%, there is a disadvantage that the toughness of the welded part is reduced. As described above, N ₂ is a component for generating a nitride in the weld metal, and the addition amount is in the range of 2 to 30%. If less than 2% is added, the amount of nitride generated is insufficient, and if more than 30% is added, the toughness decreases, which is not preferable. As will be easily understood,
When N is contained in the alloy composition of the welding wire, N ₂ in the shielding gas may be a relatively small amount even if the contained composition is selected.

The welded portion of the present invention can be formed by the above-mentioned welding method or not, by using Ti, Al components, Mo, W
All or some of the components, and further, the B, Zr, and Nb components, can be determined in the base metal to be welded. In other words, if the alloy components of the base material are known, it can be expected that a small amount of these components will be replenished therefrom. Needless to say, the weld metal is not only the components of the filler metal but also the sum of the various components of the surrounding base metal mixed and dissolved therein. However, although there is a slight difference depending on the welding method and conditions, the amount of the base metal component that is melted is not large, so that the amount of the component that can be supplemented from the surroundings is limited.

[0028]

EXAMPLE A ferritic stainless steel having an alloy composition shown in Table 1 was melted and rolled into a plate having a thickness of 1.5 mm.

Table 1 Steel sheet (% by weight, balance Fe) No. C Si Mn PS Cr Ni Mo Ti Nb N a 0.012 0.54 0.29 0.022 0.004 11.3 0.29 0.01 0.01 0.02 0.010 b 0.011 0.70 0.30 0.025 0.005 11.4 0.32 0.01 0.10 0.01 0.010 C 0.008 0.36 0.97 0.021 0.028 15.1 0.07 0.05 0.22 0.04 0.009

Separately, ferritic stainless steel having an alloy composition shown in Table 2A (Example) and Table 2B (Comparative Example) was melted, and a welding wire having a diameter of 1.2 mm was manufactured therefrom.

Table 2A Welding wire (Example) (% by weight, balance Fe) No. CSiMnPSCrTi, AlMo , WB, Zr, NbNA 0.013 0.95 0.40 0.019 0.005 16.7 1.00Ti 0.150 B 0.013 0.95 0.40 0.019 0.005 22.7 0.10Ti 0.050 C 0.013 0.95 0.40 0.019 0.005 16.7 0.10Ti 2.95W 0.240 D 0.003 0.60 0.80 0.028 0.009 19.9 0.06Ti 2.95Mo 0.100 E 0.003 0.60 0.80 0.028 0.009 19.9 0.02Al 2.95Mo 0.240 F 0.043 1.45 1.45 0.016 0.005 16.5 0.06Ti 0.025Al 2.95Mo 0.035 G 0.043 1.45 1.45 0.016 0.005 16.5 0.06Ti 0.100Al 2.95Mo 0.090 H 0.043 1.45 1.45 0.016 0.005 16.5 0.20Ti 0.110Al 2.95Mo 0.080 I 0.014 1.09 0.45 0.040 0.004 12.0 0.70Ti 0.200 J 0.014 1.09 0.45 0.040 0.004 24.5 0.70Ti 0.040 K 0.013 1.05 0.45 0.016 0.008 15.1 1.14Ti 0.003B 0.149 L 0.011 1.04 0.50 0.018 0.005 14.3 0.37Ti 0.005Zr 0.26Nb 0.034 M 0.013 0.60 0.48 0.017 0.007 13.1 0.92Ti 0.003B 0.002Zr 0.180 N 0.011 0.55 0.42 0.009 0.008 19.2 0.52Ti 0.003B 0.25Nb 0.121 O 0.009 0.45 0.44 0.007 0.007 19 .5 0.34Ti 0.003B 0.002Zr 0.105 0.070Al 0.23Nb

Table 2B Welding wire (comparative example) (% by weight, balance Fe) No. C Si Mn PS Cr Ti, Al Mo, WB, Zr, Nb NP 0.013 0.95 0.40 0.019 0.005 16.7 0.04Ti 0.150 Q 0.004 0.60 0.80 0.028 0.009 19.9 0.005Al 2.95Mo 0.150 R 0.013 0.95 0.40 0.019 0.005 16.7 1.03Ti 0.025 S 0.014 1.09 0.45 0.040 0.004 10.0 0.70Ti 0.200 T 0.050 1.45 1.45 0.016 0.005 16.5 0.75Ti 1.05Al 2.95Mo 0.180

The above steel sheet and these welding wires were combined as shown in Table 3A (Example) and Table 3B (Comparative Example), and butt welding and T-type welding were performed under the conditions shown in these tables. Done.

Table 3A Welding Conditions (Examples) No. Steel Wye Welding Arc Speed Heat Input Pulse Conditions Shielding Gas Condition Plate Current A Voltage V cm / min J / cm IP TP Ar O2 CO2 N2 He 1 A 100 15 120 750 420 1.0 97.5 2.5 0 0 0 2 A A 120 18 60 2 160 420 1.0 97.5 2.5 00 00 3 A B 120 18 60 2160 420 1.0 97.5 2.5 00 00 4 A B 120 18 60 2160 420 1.0 95.5 2.5 0 2 0 5 B B 120 18 60 2160 420 1.0 97.5 2.5 0 00 06 A C 120 18 60 2160 420 1.0 82.5 2.5 15 0 07 A D 120 18 60 2 160 310 1.5 97.5 2.5 0 0 08 A D 120 18 60 2 160 420 1.0 97.5 2.5 0 0 0 9 A D 120 18 60 2160 No pulse 97.5 2.5 0 0 0 10 A E 120 18 60 2160 420 1.0 97.5 2.5 0 0 0 11 A F 120 18 60 2160 420 1.0 97.5 2.5 0 0 0 12 A G 120 18 60 2160 420 1.0 97.5 2.5 0 0 13 A H 120 18 60 2160 420 1.0 97.5 2.5 0 0 0 14 A I 120 18 60 2160 420 1.0 82.5 2.5 3 2 10 15 A J 120 18 60 2160 420 1.0 97.5 2.5 0 0 0 16 C K 100 15 120 750 420 1.0 97.5 2.5 0 0 0 17 C L 150 20 40 4500 420 1.0 97.5 2.5 0 0 0 18 C M 120 18 60 2 160 420 1.0 97.5 2.5 0 0 0 19 C N 120 18 60 2160 420 1.0 95.5 2.5 0 2 0 20 C O 120 18 60 2 160 420 1.0 97.5 2.5 0 0 0

Table 3B Welding Conditions (Comparative Example) No. Steel Wye Welding Arc Speed Heat Input Pulse Condition Shielding Gas Condition Plate Current A Voltage V cm / min J / cm IP TP Ar O2 CO2 N2 He 1 A C 120 18 60 2160 420 1.0 97.5 2.5 0 0 0 2 A P 120 18 60 2160 420 1.0 97.5 2.5 00 00 3 A Q 120 18 60 2160 420 1.0 97.5 2.5 0 00 4 A R 120 18 60 2160 420 1.0 97.5 2.5 0 0 0 5 A S 120 18 60 2160 420 1.0 97.5 2.5 0 0 0 6 A T 120 18 60 2160 420 1.0 97.5 2.5 0 0 0 7 A C 120 18 60 2160 420 1.0 76.5 2.5 21 0 0

The grain size (JIS) of the weld metal is examined for the butt weld and the number (per 1 mm ² ) of nitride and oxide particles for large ones having a diameter of 0.5 μm or more is determined. I counted. Example No. 13
And Comparative Example No. 1, the crystal structure of the weld metal was observed with a microscope. FIG. 1 is a photomicrograph of the former, and FIG. 2 is a photomicrograph of the latter (both at a magnification of 100).

Cracks were examined for T-welded ones. As shown in FIG. 3, "T-type welding" means that the same steel plate (2) is subjected to fillet welding (3) on a flat steel plate (1) in an inverted T-shape in advance to restrain both members. The “T-type weld cracking test” is a test for measuring the degree of weld cracking of the fillet weld (4) performed at this time. .

The butt-welded one was subjected to a bending test. In the bending test, as shown in FIG. 4, one steel plate (5) was restrained and the other steel plate (6) was repeatedly used.
This is a test in which the welded part (7) bends within an angle of 0 degrees and counts how many times the bending endures. Table 4A shows the above test results.
(Example) and Table 4B (Comparative Example).

Table 4A Test Results (Examples) Nitride + oxide Grain size T-type weld crack Bending test (pieces / mm ² ) No. JIS test (number of times) 1 362 3 ９ 9 2 316 3 ８ 8 3 299 3 ８ 8 4 293 3 ８ 8 5 296 3 ８ 8 6 326 3 ８ 87 309 3 ８ 88 50 305 3 ８ 89 303 3 710 304 3 ８ 8 11 565 5 １１ 11 12 613 5 １１ 11 13 616 5 ○ 11 14 315 3 ８ 8 15 15 300 3 ８ 8 16 314 3 ○ 8 17 301 3 ○ 7 18 319 3 ○ 8 19 310 3 ○ 8 20 557 5 ○ 10

Table 4B Test Results (Comparative Example) Nitride + oxide Grain size T-type weld crack Bending test (pieces / mm ² ) No. JIS test (number of times) 1 201 × 2 223 1 × 2 314 1 × 2 4 201 1 × 2 534 1 × 2 6 11 1 × 2 736 1 × 3

Examples and comparative examples are supplemented below.

In Examples 1 and 2, the amount of heat input was changed, but no difference was obtained. In Example 4, N was supplied from the shielding gas to Example 3, but there was no particular difference in this case. Example 5 is an example in which a base material containing a relatively large amount of Ti is welded and Ti is supplied from the base material. On the other hand, Comparative Example 1
However, since the wire and the base material have low Ti contents, the production of large-sized nitrides is insufficient, resulting in poor performance. Examples 6 and 7 are examples near the upper limit or lower limit of the Ti amount, respectively. In Examples 8 and 9, the pulse conditions were changed, but there was no significant difference in the results. Example 10 is an example in which the amount of Al is near the lower limit.

In Examples 11 to 13, Ti and Al
In which a large amount of large nitrides and oxides are produced, the crystal grain size is fine, and the results of bending tests are excellent. Examples 14 and 15 are examples near the upper limit or lower limit of the Cr content, respectively. Embodiments 16 to 20 are based on B, Zr, N
This is the case where b is added alone or in combination, and the crystal grain size is fine accordingly, and the results of the bending test are excellent.

In Comparative Examples 2 to 6, all of the components of the welding wire were insufficient. Comparative Example 2 contained Ti, Comparative Example 3 contained Al, Comparative Example 4 contained N, and Comparative Example 5 contained Cr. Comparative Example 6 is an example in which C is lower than the lower limit. Comparative Example 7 is a case where the amount of CO ₂ in the shielding gas is excessive.

[0045]

The weld metal of ferritic stainless steel according to the present invention has a specific alloy composition and inclusion distribution, so that the crystal structure is enlarged as shown in FIG. 1 and FIG. Without a much finer texture than the prior art weld metal. Therefore, cracking during welding hardly occurs, and the weld metal exhibits strong resistance to bending.

The welding method of the present invention for forming such a weld metal can be achieved by appropriately selecting the alloy composition of the welding wire, appropriately selecting the shielding gas composition, and comparing the alloy composition of the welding wire with the shielding gas composition. This is achieved either by choosing both properly. Further, when the alloy composition of the ferritic stainless steel to be welded can be used, the shortage of alloy components of the wire can be compensated for, so that the implementation is easy.

[Brief description of the drawings]

FIG. 1 is a micrograph of the structure of a weld metal as seen in an example of the present invention.

FIG. 2 is a micrograph of the structure of a weld metal in a comparative example of the present invention.

FIG. 3 is a cross-sectional view including a weld for explaining a “T-type welding crack test” performed in an example of the present invention.

FIG. 4 is a cross-sectional view including a welded portion for explaining a “bending test” performed in an example of the present invention.

[Explanation of symbols]

 1, 2 steel plate 3 fillet welding performed in advance 4 fillet welding performed later 5, 6 steel plate 7 welded portion

Claims (6)

[Claims] 1. A welded portion formed by welding a base material of ferritic stainless steel using a welding wire of ferritic stainless steel, wherein, by weight%, C: 0.05% or less;
i: 2.0% or less, Mn: 2.0% or less, Cr: 15 to
25% and Ti and / or Al: 0.0
An alloy composition containing 5 to 0.5% and N: 0.05 to 0.3%, P: 0.03% or less, S: 0.01% or less, and the balance substantially consisting of Fe Having a Ti or Al nitride or oxide having a particle size of 0.5 μm
A ferritic stainless steel welded part in which the crystal grain size of the weld metal is made fine by the presence of those having a diameter of at least 250 m / mm ² or more. 2. A welded part of a ferritic stainless steel having an alloy composition containing Mo and / or W: 5.0% or less in addition to the alloy component according to claim 1. 3. The welded portion further comprises, in addition to the alloy component according to claim 1 or 2, Nb: 1.0% or less, Zr:
0.1% or less and B: A weld of ferritic stainless steel having an alloy composition containing one, two or three kinds of 0.1% or less. 4. A method for welding a ferritic stainless steel base material, wherein a ferrite stainless steel wire having any of the following alloy compositions is used as a welding wire: I) C: 0.05% Below, Si: 2.0% or less, Mn:
2.0% or less, Cr: 15 to 25%, and Ti and / or Al: 0.05 to 0.5%, N: 0.0
5 to 0.3%, P: 0.03% or less, S: 0.
0.1% or less, with the balance being substantially Fe II) In addition to (I) above, Mo and / or W:
III) In addition to the above (I) or (II), Nb: 0.5%
% Or less, Zr: 0.1% or less, and B: 0.1% or less. Contains one, two or three types as a shielding gas.
Welding is carried out using the following gas), a) Ar + (0 to 20%) O ₂ b) Ar + (0 to 20%) O ₂ + (0 to 50%) CO ₂ c) Ar + (0 -20%) O ₂ + (0-50%) CO ₂ +
(0 to 100%) He A nitride or an oxide of Ti and Al having a particle diameter of 0.5 μm or more is present at a rate of 250 pieces / mm ² or more in the weld metal portion, so that A method for welding ferritic stainless steel to obtain a weld with a fine grain size. 5. A method for welding a ferritic stainless steel base material, wherein a ferrite stainless steel wire having any of the following alloy compositions is used as a welding wire: IV) C: 0.05% Below, Si: 2.0% or less, Mn:
2.0% or less, Cr: 15 to 25%, and Ti and / or Al: 0.05 to 0.5%,
P: 0.03% or less, S: 0.01% or less, the balance being substantially Fe V) In addition to the above (IV), Mo and / or W:
5.0% or less VI) In addition to the above (IV) or (V), Nb: 0.5%
Hereinafter, Zr: 0.1% or less and B: 0.1% or less 1
Contains two, three or more species. As a shielding gas, one of the following compositions (volume%,
Welding is performed using the following gas), d) Ar + (0 to 20)% O ₂ + (2 to 30)% N ₂ e) Ar + (0 to 20)% O ₂ + (0 to 50) )% CO ₂ +
_{(2~30)% N 2 f)} Ar + (0~20)% O 2 + (0~50)% CO 2 +
To (0~100)% He + (2~30 )% N 2 weld metal, a nitride of Ti and Al or oxides in a 250 more than a particle diameter of 0.5μm to pieces / mm ² or more at a rate A method for welding ferritic stainless steel in which a welded portion having a fine crystal grain size of a weld metal is obtained by causing the welded portion to be present. 6. A method for welding a ferritic stainless steel base material, wherein a ferrite stainless steel wire having any one of the following alloy compositions is used as a welding wire: I) C: 0.05% Below, Si: 2.0% or less, Mn:
2.0% or less, Cr: 15 to 25%, and Ti and / or Al: 0.05 to 0.5%, N: 0.0
5 to 0.3%, P: 0.03% or less, S: 0.
0.1% or less, with the balance being substantially Fe II) In addition to (I) above, Mo and / or W:
III) In addition to the above (I) or (II), Nb: 0.5%
%, Zr: 0.001 to 0.01% and B: 0.
One, two or three types of 001 to 0.01% are contained. As a shielding gas, any one of the following compositions (volume%,
Welding is performed using the following gas), d) Ar + (0 to 20)% O ₂ + (2 to 30)% N ₂ e) Ar + (0 to 20)% O ₂ + (0 to 50) )% CO ₂ +
_{(2~30)% N 2 f)} Ar + (0~20)% O 2 + (0~50)% CO 2 +
To (0~100)% He + (2~30 )% N 2 weld metal, a nitride of Ti and Al or oxides in a 250 more than a particle diameter of 0.5μm to pieces / mm ² or more at a rate A method for welding ferritic stainless steel in which a welded portion having a fine crystal grain size of a weld metal is obtained by causing the welded portion to be present.