JP3165582B2 - Welding material for boron-added stainless steel and welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding material applied to the welding of stainless steel containing boron (B), and more particularly to a welding material suitable for welding a nuclear fuel storage container and a nuclear fuel transfer container, and the welding material. And a welding method using the same.

[0002]

2. Description of the Related Art Since boron is an element harmful to the weldability of a material, a welding material that does not contain boron is generally used as a welding material for welding boron-added stainless steel. Have been. However, at the time of welding, boron in the base metal may melt into the weld metal due to dilution of the base material, causing weld cracking. This weld crack is considered to be caused by boron dissolved in the weld metal forming a eutectic metal having a low melting point with iron or nickel, which is opened by contraction stress during solidification.

Therefore, as a welding rod for B-added stainless steel for preventing welding cracks, B is 0.4 to 0.7 wt% and S is 0.01%.
An austenitic stainless steel composition in which the content of P is 5 wt% or less and the content of P is 0.035 wt% or less has been proposed (JP-A-5-6918).
No. 6). Although the above-mentioned welding rod has the effect of preventing welding cracks, boron in the weld metal reacts with chromium to easily generate borides (borides), so that chromium is consumed in the vicinity and the corrosion resistance is reduced. I do.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a welding material for boron-added stainless steel which can solve the above-mentioned disadvantages, prevent welding cracks, and prevent deterioration of corrosion resistance. .

[0005]

According to the present invention, there is provided (1) a welding material for B-added stainless steel, wherein C = 0.01 to 0.08 wt%;
Si = 0.10 to 0.65 wt%, Mn = 1.0 to 2.5 wt%, P = 0.
01-0.03wt%, S = 0.001-0.03wt%, Ni = 9.0-1
1.0wt%, Cr = 19.5-25.0wt%, B = 0.1-1.3wt
%, Mo = 0.1 to 1.5 wt%, Fe = remainder, and a welding material for B-added stainless steel characterized by containing unavoidable impurities, and (2) a welding material according to (1) above, A welding method comprising welding a B-containing stainless steel joint, wherein the contents of Cr and Mo in the matrix of the molten metal satisfy the following formula. Cr + 2Mo ≧ 17.5wt%, Cr + 3Mo ≧ 18.5wt%

[0006]

[Function] When welding a B-added stainless steel with a conventional welding material that does not contain B, the base metal is melted during welding.
3030 wt% of the base metal component comes into the weld metal. Since the B content of the B-added stainless steel is several percent or less, the amount of B entering the weld metal is very small. There is a point where it is collected only between the metals and remains in the melt even when the surroundings have completely solidified due to its low melting point. At this time, the surrounding solidification shrinkage strain is applied to open, leading to cracking.

Therefore, in the present invention, B is added to the welding material positively to increase the amount of B in the weld metal, so that B is scattered almost uniformly, and B-F
e, a large amount of low melting point metal such as B-Ni is generated, and the melt is sufficiently compensated for in the opening due to shrinkage strain during solidification;
As a result, welding cracks can be prevented.

On the other hand, the corrosion resistance of the weld metal is mainly ensured by Cr. However, B in the material reacts with Cr during welding to generate bolite (Cr ₂ B), so that the surrounding Cr is consumed. As a result, the Cr content is reduced, and the corrosion resistance is reduced. Therefore, in the present invention, the decrease in corrosion resistance due to the addition of B was compensated for by the addition of Mo, and the welding crack and the decrease in corrosion resistance were successfully prevented at the same time.

The reason for adding each component of the B-added stainless steel welding material of the present invention will be described below. C
Is in the range of 0.01 to 0.08 wt%, preferably 0.01 to 0.08 wt%.
It is in the range of 0.05 wt%, more preferably in the range of 0.01 to 0.03 wt%. If it is less than 0.01 wt%, the strength becomes too low, and
If it exceeds 08 wt%, the corrosion resistance deteriorates, which is not preferable.

The amount of Si added is in the range of 0.10 to 0.65 wt%,
Preferably in the range of 0.15 to 0.40 wt%, more preferably 0.20
0.30.30 wt%. If it is less than 0.10 wt%, the deoxidizing effect is not sufficient, and if it is more than 0.65 wt%, welding cracks are likely to occur, which is not preferable.

The addition amount of Mn is in the range of 1.0 to 2.5 wt%,
Preferably in the range of 1.5-2.5 wt%, more preferably 1.5-2.5 wt%.
2.32.3 wt%. If it is less than 1.0 wt%, the deoxidizing effect and strength are not sufficient, and if it exceeds 2.5 wt%, the strength is too high, which is not preferable.

The amount of P added is in the range of 0.01 to 0.03 wt%, preferably in the range of 0.01 to 0.02 wt%, more preferably 0.01 to 0.02 wt%.
It is in the range of 0.015 wt%. To prevent weld cracking, the smaller the better, the better. However, from the experience with austenitic stainless steels, it is preferable to use 0.03 wt% or less.
The above is preferred.

[0013] The addition amount of S is in the range of 0.001 to 0.03 wt%,
Preferably in the range of 0.001 to 0.005 wt%, more preferably
It is in the range of 0.001 to 0.003 wt%. To prevent weld cracking, the smaller the better, the better. However, from the experience with austenitic stainless steels, it is preferable to use 0.03 wt% or less.
More than 001 wt% is preferred.

The amount of Ni added is in the range of 9.0 to 11.0 wt%,
Preferably in the range of 9.5 to 11.0 wt%, more preferably 10.0%
111.0 wt%. To ensure corrosion resistance, 9.
Addition of 0 wt% or more is necessary, and in order to suppress the cost and not to deteriorate the drawability, it is preferable that the content be 11.0 wt% or less.

The amount of Cr added is in the range of 19.5 to 25.0 wt%,
Preferably in the range of 20.5 to 25.0 wt%, more preferably 21.5
225.0 wt%. It is a component necessary to ensure corrosion resistance, and it is preferable to determine it in relation to the amount of Mo in order to prevent general corrosion and crevice corrosion, but from the viewpoint of cost, it should be 19.5 wt% or more according to JIS standards. It is preferable to set the content to 25.0 wt% or less, which does not impair the drawability.

The amount of Mo added is in the range of 0.1 to 1.5 wt%.
Preferably in the range of 0.5-1.5 wt%, more preferably 0.8-1.5 wt%.
It is in the range of ~ 1.2 wt%. Like Cr, it is a component that affects corrosion resistance, and is particularly effective against chlorine. Upper limit 1.
5 wt% is the maximum B content (1.3 wt%)
%) Enters the weld metal by the amount of decrease in effective Cr [about 3.
3 wt% (1.3 × 2.5)] was set to be supplemented with Mo.
The lower limit of 0.1 wt% is the B content (about 0.3 wt%) from the base metal that enters the weld metal by dilution of the base metal during normal welding.
Was set to supplement with Mo.

The amount of B added is in the range of 0.1 to 1.3% by weight, preferably in the range of 0.2 to 1.0% by weight, more preferably 0.3 to 1.0% by weight.
It is in the range of 1.0 wt%. If it is less than 0.1 wt%, welding cracks are liable to occur. 1.3 wt% is the upper limit of the base metal. It is not necessary to increase the base metal dilution even further, and the range is set so that welding cracks do not occur.

In particular, regarding the addition amounts of Cr and Mo,
r + 2Mo ≧ 17.5wt% and Cr + 3Mo ≧ 18.5wt%
By setting the range, the above-mentioned effect can be further ensured. The overall corrosion rate was (Cr + 2
Mo) (see Hideaki Yuki and Hiroo Nagano, "Sumitomo Metals" Vol. 41, No. 3 (1989.7), page 377, FIG. 7), and the reduction in crevice corrosion is the amount of (Cr + 3Mo). Can be organized. (Hideaki Yuki, Hiroo Nagano, "Anti-corrosion Technology" Vo
l.37, No.12 (1988.12), page 729, see Fig. 9 and Fig. 10)

The following is an example of the composition of the B-added stainless steel suitable for applying the welding material of the present invention. C = 0.015-0.08 wt%, Si = 0.2-0.6 wt%, Mn =
1.2 to 2.0 wt%, P = 0.015 to 0.03 wt%, S = 0.001 to
0.002wt%, Ni = 9.1-13.5wt%, Cr = 19.6-24.5
wt%, B = 0.5-1.3 wt%, Mo = 0.01-0.2 wt%, F
e = remainder.

[0020]

EXAMPLES (Example 1) B-SUS304 steel containing B (Steel 2 to Steel 8 in Table 1)
And SUS304 steel without B added (Steel 1 in Table 1)
Welding materials with different amounts of B added (materials a to f in Table 2)
FIG. 1 shows the results of TIG welding for fillet welding and welding cracks. In addition, steel 5, steel 7, and steel 8 in Table 1
Chemical composition and / or (Cr + 2M
o) and (Cr + 3Mo) are out of the scope of the present invention
It is an example. As is clear from FIG. 1, B = 0.1 to 1.5 wt.
% Indicates that no weld cracking occurs. The cause of the cracks is due to the low melting point eutectic metal generated during welding, and it is known that stainless steel containing B is produced (see “Stainless Steel Handbook”, p. 354).

[0021]

[Table 1]

[0022]

[Table 2]

Example 2 Next, B-added stainless steel B-SUS304 ( chemical composition)
But C: 0.013, Si: 0.39, Mn: 1.61, P: 0.031, S: 0.002, Ni:
10.08, Cr: 19.59, B: 0.58, Mo: 0.49 ) A welding material containing B-free stainless steel SUS304 (Steel 1 in Table 1) vertically standing on the surface of B, containing 0.12 wt% of B and 0.62 wt% of Mo Fillet welding was performed using (material b in Table 2) and a welding material to which B and Mo were not added (material a in Table 2).
The cross section of the weld metal was examined under a microscope.

FIG. 2 shows a welding material b containing B and Mo.
It is a microscope photograph of 3 times, 100 times, and 500 times of the weld metal using the material. As is clear from this photograph, no weld crack was observed. Further, FIG. 3 shows that the welding material using the welding material “a” without B and Mo is 5 times as large as the welding metal,
It is a micrograph at the magnification of 00 and 500 times. As is clear from this photograph, weld cracking was observed.

(Embodiment 3) Using the materials listed in Table 1, a wire cut out of the same material was used as a welding material, and the current was 100 ± 5 A, the voltage was 10 ± 2 V, and the speed was 8 ± 2 cm / min by TIG welding.
Specimens collected by machining from the welded joints welded under the conditions of
mb + 500 ppm Cl ^-1 ) to maintain the state where the test liquid surface comes into contact with air and air can freely enter the test liquid (referred to as air saturation), the test temperature is 80 ° C, and the test time is 720 hours The overall corrosion rate test was performed, and the results are shown in FIG. As is clear from FIG. 4, (Cr
+ 2Mo) When the amount is 17.5 wt% or more, it can be seen that substantially no overall corrosion occurs.

The abscissa in FIG. 4 indicates the amount of (Cr + 2Mo) in the matrix. Bolite (Cr ₂ B)
Since the amount of decrease in Cr due to formation is approximately 2.5 times the amount of B added, it is estimated that 2.5 times the amount of Cr in Table 1 is present in bolite, and the amount of Cr in the matrix is Is
Table 1 shows the value obtained by subtracting the amount of Cr in the bolite from the amount of Cr in the welding material. The amount of (Cr + 2Mo) was determined from the amount of Cr in the matrix and the amount of Mo in the welding material.
In FIG. 4, the results of four experiments are shown for welding material 3 in Table 1, three times for welding material 6 , and two for other welding materials.
The results of the experiments are also shown.

Example 4 A crevice corrosion weight loss test was performed under the same conditions using a test piece prepared under the same conditions as in Example 3, and the results are shown in FIG. As apparent from FIG. 5, the amount of (Cr + 3Mo) in the matrix was 18.5 wt%.
In the above case, it can be seen that crevice corrosion does not substantially occur. The horizontal axis in FIG. 5 indicates (Cr) in the matrix.
+ 3Mo). The calculation was performed according to Example 3. In addition, in FIG. 5, the welding materials in Table 1 each show the results of two experiments.

[0028]

According to the present invention, it is possible to provide a welding material capable of securing welding cracks and corrosion resistance by employing the above-described structure.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the amount of B in a weld metal and cracks according to Example 1.

FIG. 2 is a structural diagram of a welded portion using a welding material containing B and Mo in Example 2.

FIG. 3 is a structural diagram of a welded portion using a welding material containing neither B nor Mo in Example 2.

FIG. 4 is a diagram showing the relationship between the overall corrosion rate and the amount of (Cr + 2Mo) in a matrix in Example 3.

FIG. 5 is a diagram showing the relationship between crevice corrosion loss and the amount of (Cr + 3Mo) in a matrix in Example 4.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yukihiro Kawai 2-1-1 Shinhama, Arai-machi, Takasago City, Hyogo Prefecture Inside the Takasago Research Laboratory, Mitsubishi Heavy Industries, Ltd. 1-1, Mitsubishi Heavy Industries, Ltd., Kobe Shipyard (72) Inventor Shigeru Matsumoto 1-1-1, Wadazakicho, Hyogo-ku, Kobe, Hyogo Prefecture, Japan Inside Kobe Shipyard, Mitsubishi Heavy Industries, Ltd. Kobe, Hyogo-ku, 1-1-1 Wadazaki-cho Mitsubishi Heavy Industries, Ltd. Kobe Shipyard (56) References JP-A-5-69186 (JP, A) JP-A-58-202993 (JP, A) JP-A 4-157090 (JP, A)

Claims (2)

(57) [Claims] 1. A welding material for B-added stainless steel, wherein C = 0.01 to 0.08 wt%, Si = 0.10 to 0.65 wt%, Mn
= 1.0-2.5 wt%, P = 0.01-0.03 wt%, S = 0.001-
0.03wt%, Ni = 9.0-11.0wt%, Cr = 19.5-25.0wt
%, B = 0.1-1.3 wt%, Mo = 0.1-1.5 wt%, Fe
= Welding material for B-added stainless steel, characterized by containing the balance and unavoidable impurities. 2. A welding method for welding a B-containing stainless steel joint using the welding material according to claim 1, wherein the contents of Cr and Mo in the matrix of the molten metal satisfy the following expression. Cr + 2Mo ≧ 17.5wt% Cr + 3Mo ≧ 18.5wt%