JP3155148B2 - Gas shielded arc welding wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to welding which is used for welding low induction activated ferritic steel for the first wall of a fusion reactor and which has excellent high-temperature creep strength and toughness and also has excellent crack resistance during welding. The present invention relates to a gas shielded arc welding wire from which a metal can be obtained.

[0002]

2. Description of the Related Art A fusion reactor has a track record as an experimental reactor and has already achieved critical plasma conditions. At present, SUS316 is used as the first wall material, but SUS316 cannot be used at the neutron irradiation amount expected in a commercial reactor due to the problem of void swelling. Therefore, SUS316
Or HT-9 steel (12Cr-1 steel) which has a low void swelling due to its ferrite system.
Mo-WV) has been developed. Furthermore, since the reduction of radioactive contamination at the time of repair during use or disposal after shutdown is extremely economically advantageous, a low activation material with less induced activation has been required. For this reason, Ni, C, which are ferritic steel and have high induced activation elements,
Steel in which u, Mo, Nb, Co and the like are reduced as much as possible is being studied.

Japanese Unexamined Patent Publication (Kokai) No. 62-238352 proposes a ferrite steel for a fusion reactor excellent in high-temperature strength for this purpose, but does not mention welding materials. Japanese Patent Application Laid-Open No. 3-174998 proposes a welding wire for a low-induction activated ferritic steel as a welding material necessary for putting such a ferritic steel into practical use, and is excellent in high-temperature strength characteristics and toughness. Although a welding wire for providing a weld is disclosed, it does not ensure sufficient crack resistance. Further, JP-A-1-
Japanese Patent Application No. 215490 discloses that 11 to 13% Cr is used in an amount of 0.1%.
A welding wire for Cr-Mo based low alloy steel which obtains a weld having high creep strength and high toughness by containing from 02 to 0.08% has been proposed, but what pays attention to the balance of C, N and B is disclosed. No welding wire with improved high-temperature strength, toughness, and crack resistance is disclosed.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides a weld metal excellent in crack resistance while obtaining sufficient high-temperature strength and toughness for low induction activated ferritic steel. It is intended to provide a welding wire that can perform the welding.

[0005]

DISCLOSURE OF THE INVENTION The present invention restricts alloying elements harmful to stimulated activation, and further comprises C, Si,
Appropriate amounts of Mn, W, V, Ta are added, and C, B, N
By optimizing the balance of off together with toughness is excellent, there is feature in that to both high-temperature strength and resistance to cracking, and it is subject matter, with reduced induction activation by neutron
For gas shielded arc welding of ferritic steel
A wire, C: 0.02 to 0.12%, Si:
0.03 to 0.40%, Mn: 0.10 to 1.60%,
Cr: 8.0 to 12.0%, W: 1.3 to 2.4%,
V: 0.05 to 0.30%, Ta: 0.05 to 0.12
%, B: 0.0010 to 0.0035%, N: 0.01
8 to 0.033%, O: 0.002 to 0.007%, and satisfies 0.08% ≦ C + N + 10B ≦ 0.16%, and further contains Mo, Nb,
A gas shielded arc welding wire characterized in that Co, Ni and Cu are limited so that Mo + Nb + Co + Ni + Cu ≦ 0.12%, and the balance consists of Fe and unavoidable impurities.

[0006]

One of the features of the present invention is that by controlling the balance of C, B, and N within an appropriate range, it is possible to obtain a weld metal having good crack resistance and high temperature strength. It is in. Hereinafter, reasons for adding each component of the welding wire according to the present invention and reasons for limiting the components will be described.

C: 0.02 to 0.12% C acts as a solid solution strengthening element and forms carbides to improve the high temperature creep strength. Furthermore, it is one of the austenite stabilizing elements, and suppresses the formation of coarse δ ferrite and improves toughness. In order to obtain the above effects, it is necessary to contain 0.02% or more. However, if the content is too large, the hardening of the weld metal is caused and the cracking resistance is deteriorated. is there. Therefore, the range is determined as described above.

Si: 0.03 to 0.40% Si is an effective deoxidizing element and is essential for deoxidizing a weld metal, and is also effective for improving welding workability. However, when the content is high, toughness is deteriorated. To obtain the effect of Si, 0.03% or more is required. If it is added in excess of 0.40%, the toughness of the weld metal deteriorates significantly.
The range was determined as described above.

Mn: 0.10 to 1.60% Mn is an indispensable element for enhancing hardenability and ensuring high strength. It is also effective in improving toughness. In order to obtain this effect, 0.10% or more is necessary. If it exceeds 1.60%, the hardenability becomes excessive, and the hardening of the weld metal significantly deteriorates the cracking resistance. I decided.

Cr: 8.0 to 12.0% Cr is an indispensable element in terms of ensuring high-temperature oxidation resistance, corrosion resistance and strength of the weld metal. If it is less than 8.0%, the above effect is not sufficient, and if it exceeds 12.0%, δ ferrite tends to precipitate and the toughness is greatly deteriorated. Therefore, the range is determined as described above.

W: 1.3 to 2.4% W is a solid solution strengthening element and significantly improves high temperature creep rupture strength. In particular, in welding low induction radioactive steel,
Since Mo, which can be expected to have the same effect, is a stimulated activation element and needs to be restricted, W must be used effectively. If the content is less than 1.3%, the effect of improving the strength is not sufficient, and if the content exceeds 2.4%, the toughness is reduced. Therefore, the range is set as described above.

V: 0.05 to 0.30% V combines with C to precipitate fine carbides and improve the creep rupture strength. The effect becomes remarkable at 0.05% or more, and when it exceeds 0.30%, the toughness is reduced, the hardening of the weld metal is caused, and the crack resistance is also deteriorated.

Ta: 0.05 to 0.12% Ta enhances the high-temperature creep strength by precipitation strengthening as TaN and TaC, and the solid solution Ta also has the function of improving the toughness. To obtain these effects, 0.05% or more is required. On the other hand, if it is added in excess of 0.12%, the creep rupture strength is conversely reduced and the toughness is also reduced. Therefore, the range is set as described above.

B: 0.0010 to 0.0035% B is added in a small amount to enhance hardenability and to refine the microstructure.
It is effective in improving creep rupture strength and toughness. If the amount is excessive, the weld metal is remarkably hardened, resulting in a decrease in ductility and deterioration in crack resistance. Therefore, it is necessary to pay sufficient attention to the amount of addition. The content in the wire is 0.0010
If the content is 0.0035%, remarkable hardening of the weld metal is not caused, and the high-temperature strength and toughness can be improved. Therefore, the range is set as described above.

N: 0.018 to 0.033% N is an induced activation element and is an element to be restricted low for low induction activated ferritic steel, but is indispensable for securing high-temperature creep strength. Element. Therefore, an appropriate amount is added to the wire of the present invention. N is T
It forms fine precipitates such as aN and VN, remarkably improves high-temperature creep strength, suppresses the formation of δ ferrite, and is effective in improving toughness. To obtain this effect, 0.018% or more is necessary. If the content exceeds 0.033%, the ductility is reduced due to the remarkable hardening of the weld metal, and the crack resistance is deteriorated. Further, since the toughness significantly decreases, the range is determined as described above.

O: 0.002 to 0.007% O deteriorates the toughness of the weld metal, so it must be kept low. However, if the content is less than 0.002%, the welding workability is impaired, so the range is determined as described above.

0.08 (%) ≦ C + N + 10B ≦ 0.16 (%) C, N, and B all improve the high-temperature creep strength as described above, but if too much, carbides and carbonitrides become excessive and the weld metal becomes excessive. Is an element that causes the hardening of the weld metal and degrades the crack resistance of the weld metal. Therefore, it has been found from various experimental results that it is important to maintain a proper balance of C, N and B in order to achieve both high temperature creep strength and crack resistance.
C + N + 10B has a kind of carbon equivalent meaning and can be used as an index for determining the high-temperature creep strength and the crack resistance of the weld metal (hardening characteristics of the weld metal). C +
If N + 10B is less than 0.08%, the hardenability of the weld metal is insufficient, and the effect of improving high temperature creep cannot be obtained. on the other hand,
If C + N + 10B exceeds 0.16%, the weld metal is significantly hardened, and the weld metal is liable to crack. For this reason C
The range of + N + 10B was determined as described above.

Mo + Nb + Co + Ni + Cu ≦ 0.12 (%) Mo, Nb, Co, Ni and Cu are all induced activation elements and need to be regulated. It is desirable not to add other than as low as possible and to contain as inevitable impurities. The total amount was set to 0.12% or less.

Although not particularly limited, it is effective to keep inevitable impurities such as P and S low from the viewpoint of securing toughness and preventing embrittlement during use. Both P and S are desirably 0.005% or less.

The wire having the above chemical composition can be used for gas shielded arc welding such as TIG welding, MAG, and MIG welding. Usually, the wires used for these weldings are often plated with Cu to prevent rust and ensure electrical conductivity. However, the wires of the present invention use Cu plating to reduce Cu, which is an induced activation element. Must not go.
For this reason, in the management of the wire, it is necessary to pay sufficient attention to the state of packaging and storage, and to pay attention to the occurrence of rust and the like. In addition, the wire of the present invention can be used for various low-induction activated ferritic steels, and can exert a great effect particularly by welding low alloy steel containing 8 to 10% Cr.

[0021]

Next, examples of the present invention will be described. Table 1 and Table 2
The chemical composition of the wire according to this example and various test results are shown in FIG. Wire symbols A-1 to A-8 are wires of the present invention,
B-1 to B-9 are comparative example wires. Weld metals were prepared from these wires under the welding conditions shown in Table 3 in accordance with JIS Z3316, and the mechanical properties were investigated.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

A mild steel was used for the test plate, and the groove face was buttered with a wire to be tested. The welded test material was subjected to a post-heat treatment at 740 ° C. × 1 hr in an electric furnace to
A Charpy impact test specimen (JIS Z31114) was collected from the position indicated in ISZ3316. Similarly, a creep rupture test piece was sampled according to the procedure for collecting a tensile test piece. The impact test was performed at 0 ° C., and the average value of three absorbed energies was determined. The creep rupture test was performed at 600 ° C., and the creep strength for 10,000 hours was determined, and a value of 100 N / mm ² or more was determined to be good.

Further, JIS Z
A U-shaped weld crack test piece shown in FIG. 1 was prepared according to 3157, and a weld crack test was performed under the welding conditions shown in Table 5. The slit interval of the test plate is 1 mm, and the test plate temperature is 200 ° C.
It was repeated three times. After 48 hours from welding, surface cracks and cross-sectional cracks were examined. Those having neither surface cracks nor cross-sectional cracks were evaluated as good, and those having cracks were evaluated as poor.

[0027]

[Table 4]

[0028]

[Table 5]

Symbols A-1 to A-8, which are the wires of the present invention, contain C, Si, Mn, W, V and Ta in appropriate amounts,
In each case, the absorption energy at 0 ° C. was 130 J or more, indicating good toughness. Furthermore, the balance of C, B, and N is good, the creep rupture strength is 100 N / mm ² or more, and even in a U-shaped welding crack test by preheating at 200 ° C., no cracks are generated and good crack resistance is obtained. showed that.

On the other hand, the wire B-1 had good creep rupture strength, but C + N + 10B was too high, so that a crack was generated in a U-shaped welding crack test. Conversely, wire B-2 is C +
Since N + 10B was low, the creep rupture strength was low.
In addition, wire B-1 had poor welding workability because Si was too low, and B-2 also had poor toughness because Si was too high.

The wire B-3 had extremely low toughness and poor crack resistance due to too high C and W, and low creep rupture strength due to low Cr. Further, the welding workability was poor due to the low O content. Wire B-4 is composed of Mn and O
, The toughness was low and the crack resistance was poor. Further, the creep rupture strength was low due to the small amount of W. Further, the wire B-5 had a low C and a low Ta, so that the creep rupture strength was low. Furthermore, the toughness deteriorated due to excessive Ta.

The wire B-6 had low creep rupture strength and poor toughness because Mn and V were too low. Also, welding workability was inferior because Mn was too low. Wire B-7 is Cr
And V were too large, they exhibited low toughness and poor crack resistance. Further, since B was low, the creep rupture strength was also low.
Wire B-8 was poor in toughness and crack resistance due to excessive B. Further, the creep rupture strength was also low because N was too low. Wire B-9 had low Ta and too high N, and thus had poor toughness and crack resistance.

[0033]

As described in detail above, according to the present invention,
It has excellent high-temperature strength and toughness in welding of various low-induction activated ferritic steels, and it is possible to obtain weld metal with excellent crack resistance, which contributes to the practical application and safety of fusion reactors. Is big.

[Brief description of the drawings]

1A and 1B are views showing the shape of a U-shaped weld crack test plate used for a crack resistance test, wherein FIG. 1A is a plan view and FIG. 1B is a view A of FIG.
-A sectional view

Continuation of front page (72) Inventor Kazushi Hamada 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (56) References JP-A-3-174998 (JP, A) JP-A-1 -215489 (JP, A) JP-A-5-269590 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 35/30

Claims (1)

(57) [Claims] (1) A neutron beam-induced reduced activation.
For gas shielded arc welding of ferritic steel
Wire : C: 0.02 to 0.12% Si: 0.03 to 0.40% Mn: 0.10 to 1.60% Cr: 8.0 to 12.0% W by weight% 1.3 to 2.4% V: 0.05 to 0.30% Ta: 0.05 to 0.12% B: 0.0010 to 0.0035% N: 0.018 to 0.033% O : 0.002% to 0.007%, and 0.08% ≦ C + N + 10B ≦ 0.16%, and Mo, Nb,
A gas shielded arc welding wire characterized in that Co, Ni and Cu are limited to Mo + Nb + Co + Ni + Cu ≦ 0.12%, and the balance consists of Fe and unavoidable impurities.