JPS62158845A - High-strength ni-base alloy excellent in corrosion resistance - Google Patents

Abstract

PURPOSE:To improve stress corrosion cracking resistance and hydrogen cracking resistance by adding a limited amount of Cu and by specifying the relationship among the additive quantities of Cr, Mo, and W as well as the relationship between the additive quantities of Mo and W in an Ni-base alloy having a specific composition. CONSTITUTION:The alloy has a composition consisting of, by weight ratio, <=0.1% C, >0.05-0.30% Si, <=2.0% Mn, <=0.030% P, <=0.0050% S, 45-60% Ni, 15-30% Cr, Mo and/or W so that Mo and W are <16% and <=5.0%, respectively, and inequality I is satisfied, 0.30-3.0% Cu, <=0.050% Ti, 0.30-3.0% Nb, <=1.0% Al, >0.050-0.25% N, and the balance Fe with inevitable impurities. Moreover, in the above composition, conditions represented by inequality II are satisfied. Further, Co, one or more elements among V, Ta, Zr, and Hf, and one or more elements among rare earth elements, Mg, Ca, and Y are incorporated, if necessary. This high-strength Ni-base alloy is applicable to material for oil well tubes, etc.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applicable to a corrosive environment, which is more corrosive than the so-called sour gas environment (H2S-Co2-C1- environment), which has attracted attention in the past. Sulfur (,S') is Fe
High-strength Ni for oil country tubular goods that has good resistance to stress corrosion cracking and hydrogen cracking even in a sour gas environment where it is mixed in as a single substance rather than as a sulfide such as S or NiS.
It concerns base alloys.

<Conventional technology and its problems> The energy situation in recent years has reached the point where oil wells have to be dug deeper and wells have to be drilled in sour gas environments.
Although expensive, high-strength, high-durability Ni-based alloys for oil country tubular goods have been developed and are now being applied, as they can withstand the harsh environments mentioned above (for example, Japanese Patent Laid-Open No. 54-107
(See Publication No. 828 and Japanese Unexamined Patent Publication No. 127831/1983)
.

However, according to recent oil well information, in addition to the above-mentioned sour gas environment, which has been considered to be severely corrosive, it has been found that there is also an environment in which sulfur (S) is mixed as a single substance. In such an environment, it has become clear that even the sour gas resistant Ni-based alloys proposed so far are not fully satisfactory in terms of corrosion resistance.

To elaborate more on this point, as explained earlier,
In recent years, new oil and gas wells have tended to have environments in which not only oil and natural gas but also corrosive gases such as H2S and Co2 are mixed together with water and salts (C7-, Br-, etc.). According to the analysis results of these environmental components conducted on the ground, recently, sulfur (B) has been found mixed with the above corrosive gases, water, salts, etc. as a simple substance (not in the form of sulfides such as FeS or NiS). ), the existence of oil wells that belong to a new environment has also been confirmed. Sulfur (S) that exists in such an environment is H
As shown by the formula 2SX2H2S + Bx-0, polysulfide (H2Sx)
It is also said that S exists as a simple substance, but depending on the temperature and pressure (particularly H2S partial pressure), 4 S + 4 N20 '3 3 H2S + H2S
It cannot be denied that it is in the form of S or H2SO4 as shown in the formula O4.

Among these, H2Sx has the function of increasing the H2S concentration as a H2S gas server (storage role), and on the other hand,
H2SO, has the effect of lowering the pH.

By the way, in order to confirm these phenomena, the present inventors also conducted experiments under H2S -Co2- Ct- environment and H2S -Co2
-ct--s We conducted a research experiment on the difference in corrosion resistance that exists in Ni-based alloys (austenitic alloys) on a metal platter, and the results showed that N
Sulfur (S) has different effects on the corrosion resistance of i-based alloys.
Although the fact that the presence of sulfur (S) significantly deteriorates the corrosion resistance of Ni-based alloys has been confirmed, the corrosion mechanism when sulfur (S) coexists has not been clearly elucidated, and can be broadly classified into ■ H2Sx → H2S reservoir theory. Formula r H2S+
Polysulfide (H) according to 5X-1#H2SXJ
2Sx ) is generated in a high temperature environment and acts as a reservoir for H2S, so when H2Sx comes into contact with the material, it acts in the same way as in a high H2S environment.■ Low pH theory due to H2SO4 Even in an environment with only simple S in the absence of H2S. , if water is present, H2S is generated and H2SO4 is also generated at the same time according to the formula [4S + 4H2003H2S + H2SO4J, which lowers the pH.This is beyond the realm of speculation, as one of the two theories is likely. I couldn't.

<Means for solving the problem> From the above-mentioned viewpoint, the present inventors have developed not only a normal sour gas environment (H2S + Co2- C1- environment) but also a method in which sulfur (S) is mixed alone. As a result of further research in order to provide a high-strength alloy with sufficiently satisfactory corrosion resistance even in such environments, the following knowledge was obtained. That is, (a) In an environment where elemental sulfur (S) is further mixed into the sour gas environment, there is a corrosion form that is different from the corrosion mechanism of Ni-based alloys in the conventional sour gas environment, and elemental S is Depending on the pressure (particularly H2S partial pressure), "SX, -4
-H2S * H2Sx According to the reaction of J, three states (5x-
1, H2S and H2Sx), and 5X
-1 If free sulfur (S) or H2Sx is present, it will locally adhere to oil country tubular members, causing significant pitting corrosion in that area and causing stress corrosion cracking; (b) Conventional sour gas In the environment, there is almost no change in the form of sulfur (S) as shown in the reaction formula above, and therefore, long-awaited corrosion due to 5X-1 or H2Sx does not occur, but simple sulfur (S) may be mixed in. The reason why the above-mentioned peculiar form of corrosion occurs in a sour gas environment is that
4 S + 4 N20j 3H2S + H2SO,
A reaction called J also takes place, and at the same time H2S is generated, H2
(C) In order for OCTG materials to exhibit sufficient corrosion resistance in an environment exhibiting such a unique form of corrosion, conventional It is essential to form a protective film that is stronger and has better repairability than the corrosion-resistant film formed on Ni-based alloys for sour gas resistance. It is necessary to take measures to prevent corrosion from progressing and prevent stress corrosion cracking.
(d) The protective film strength and repair ability of conventional Ni-based oil country tubular materials in a sour gas environment are generally similar to that of Cr.

The improvement is proportional to the content of Mo and W, but in an environment containing elemental S, the role of Cu is even more important in addition to these. When the environmental temperature is 25
If the temperature is below 0℃, Cr (%) + l0M0 (%) + 5 W (%≧14
0, and if the environmental temperature is higher than 300℃, Cr@) + 10M0 (%) + 5WC@≧180 is not ensured, otherwise a sufficiently tough protective film with good repairability will be formed. (e) Furthermore, as mentioned in item (C) above, measures to strengthen the protective film alone are insufficient to alleviate the unique forms of corrosion and improve the corrosion resistance of alloy members; It is essential to improve the internal quality to prevent the It is extremely effective to suppress precipitation and its clustering; (f) Normally, high Cr-Mo based N
Even if an attempt was made to strengthen the Ni-based alloy with I (which is inexpensive), it could not prevent the stress corrosion cracking resistance from being adversely affected, but if the Ti content in the Ni-based alloy is particularly suppressed to below 0.050%, Solid solution strengthening and work hardening ability due to N will be dramatically improved, and this and Cr (%) + 10 Mo
(%) + 5 W (When combined with the component balance condition of d≧140, a Ni-based alloy having both excellent stress corrosion cracking resistance and high strength can be obtained.

This invention was made based on the above knowledge, and the Ni-based alloy is made of: C: 0.10% or less, S: 〇, over 05 to 0.30%.
%, Mn: 2.0% or less, P: 0.030%
Hereinafter, S: 0.0050% or less, Ni: 45 to 60%, Cr215 to 30%, and one or more of Mo and W.

Mo is less than 16%, W is less than 5.0%, and 12≦Mo(%)++W (an amount satisfying <16), Cu: o, 30 to 3.0%, Ti: o, 050
% or less, Nb: 0.30-3.0%, Ae: 1
．． 0% or less, N: more than 0.050 to 0.25%, and if necessary, C○ 50% or less, V 1Ta, Zr, and Hf 1 and 2 each 1.0
% or less, Rare earth elements: O, l O or less, My: 0.10 or less, ca: O, l O or less, Y: 0.20 or less, including one or more of the following, Fe and others Unavoidable impurities: consisting of the remainder, Cr (%) + 10 Mo (%) + 5 W (%) ≧
By configuring the component composition to satisfy the formula 140, sulfur (
It is characterized by the fact that it exhibits extremely high stress corrosion cracking resistance and hydrogen cracking resistance and high strength even in a sour gas environment of about 250°C or less when containing S) as a single substance. be.

Next, the reason why the composition of the Ni-based alloy is numerically limited as described above in this invention will be explained.

a) C When the C content in the alloy exceeds 0.10%, the amount of M60 type carbides (where M is Mo, Ni, Cr, W, etc.) increases significantly, deteriorating the ductility and toughness of the alloy. Therefore, the C content was set at 0.10% or less. It is recommended to reduce the C content to 0.020% or less, and in particular, reduce the C content to 0.020% or less.
When suppressed to 0% or less, ductility, toughness, and corrosion resistance are even more significantly improved.

b) 5i Sl is added because it is an effective component as a deoxidizing agent, but if it is added in a large amount, σ, Pl Laves
Intermetallic compounds (hereinafter referred to as b), which are unfavorable for the ductility and toughness of the phase, are likely to be formed. Moreover, if the S1 content is particularly 0.30
If the ratio exceeds 1, microsegregation during solidification is promoted, and the formation of the M, C, and P phases tends to be significantly promoted. For this reason, the upper limit of S1 content is set to 0.30.
%, but if the content is reduced to 0.10% or less, the effect of suppressing grain boundary precipitation of carbides is added, and ductility, toughness, and corrosion resistance are further improved. On the other hand, the S1 content was set to 0.
Since reducing the S1 content to 0.05% or less would require troublesome operations in the production of the alloy, the S1 content was set at a range exceeding 0.05%.

) Mn Mn is a component usually added as a desulfurizing agent, but
If the content exceeds 2.0%, TCP-phase acid formation may occur, so the f'iMn content in the alloy of the present invention was set at 2.0% or less.

Engineering) P and S P and S are impurities that inevitably enter the alloy, and if they exist in large quantities in an alloy, they reduce hot workability due to grain boundary segregation and also deteriorate corrosion resistance. The P content was determined to be 0.030% or less, and the S content was determined to be 0.0050% or less.

However, when the S content is suppressed to 7% or less, the hot workability of the alloy is dramatically improved, and when the P content is suppressed to 0.0030%, the hydrogen cracking resistance of the alloy is significantly improved. Therefore, it is preferable to reduce the contents of ljP and S to such a level.

In addition, Figure 1 shows that the parallel part is 4.0 mm from an alloy prepared by changing only the amount of P within the composition specified by this invention and made high strength by cold working of about 30%. G in φ
L is 30. A test piece of H2S -5% NaC was taken and saturated with H2S at 10 atm.
A tensile test was conducted at a constant strain rate of I x 10-71/see with a cathode current of 5 mA/cm" applied in a 4 solution (25°C) to evaluate its hydrogen cracking resistance. .

In addition, FIG. 2 shows that Sl in the components defined by this invention.
A high temperature ductility test was conducted at 1150°C (test piece 10mtttφ, strain rate: 11/s).
ee) to show the effect on hot workability.

It is clear from FIGS. 1 and 2 that it is preferable to reduce the P and S contents to extremely low levels if possible.

e) Ni The alloy of the present invention contains MolCr and W, which are elements with good solid solution strengthening and work hardening ability, in the Ni matrix.

The basic rule is to add Nb, etc. to strengthen it, but since adding large amounts of the above elements leads to destabilization of austenite, the lower limit of the content is set at 45%, which is the amount of Ni that is sufficient to stabilize the austenite base. It was determined that On the other hand, Ni itself is an element that improves work hardening ability, but if it is contained in excess of 60%, hydrogen cracking resistance deteriorates.
The upper limit of the Ni content was set at 60 inches.

Strength) Cr Cr is a component that improves the corrosion resistance and strength of the alloy together with Mo, and this effect is more noticeable when it is contained in a proportion of 15% or more. On the other hand, if Cr exceeds 30%
When containing TCP, the hot workability of the alloy decreases, and TCP
Since phases are less likely to form, the Cr content? 'i15
It was set at ~30%.

G) Mo and W These components have the effect of significantly improving the strength and corrosion resistance of the alloy, especially the pitting corrosion resistance, in coexistence with Cr, so one or more of these components may be added. If the content is less than 12 (Mo (%) 41 - W (%)), the desired effect cannot be obtained from the above action, and on the other hand, Mo
If the content is 16 or more, the W content exceeds 5.0%, or the value of (Mo (%) + 4rw (a)) is 16 or more, a large amount of Cr is added. This leads to the destabilization of the austenite base as seen in
W is 5. The content was determined to be less than ◯ and satisfy 12≦Mo(%)+−)W(%)<16.

Cu) In a sour gas environment where sulfur (S) is observed alone, Cu, along with Cr and MolW, is an extremely effective component for improving corrosion resistance, but if the Cu content is less than 0.30%, the desired corrosion resistance cannot be obtained. On the other hand, since the effect is saturated even if Cu is contained in an amount exceeding 3.0%, Cu
The content was determined to be between 0.30 and 3.0.

i) Ti In order to effectively strengthen the N-based alloy of the present invention with N, it is necessary to suppress the formation of coarse TiN as much as possible, but if the Ti content exceeds 0.050 Ti, the coarse TiN Therefore, it was decided that the T1 content should be suppressed to 0.050% or less.

e) Nb Nb is a component that significantly improves the corrosion resistance of the alloy in a sour gas environment where sulfur (S) is found alone, and also has a stabilizing effect on C, and also contributes to increased strength. However, if the content is less than 0.30%, the desired effect cannot be obtained in the above action, while if the content exceeds 3.0%, TCP phase is likely to be generated.
The b content was determined to be between 0.30 and 3.0.

In addition, FIG. 3 shows that Nl in the components defined by this invention.
) The effect of Nb on stress corrosion cracking resistance was examined by changing only the amount of Nb. The strength of the sample material (0.2% yield strength)
After making a test piece of 4.0 mm φ and GL: 30 mm using a test piece with a constant value of 100 to 105 krf/*m'', 20% NaCt-0.5% CH3CoOH-l
9 /lS-10atmH2fEt-2QatmC
○Measure the elongation by carrying out a constant strain rate tensile test of l x 10-71/crown in the solution of 2 (250℃), and evaluate the stress corrosion cracking resistance by comparing this with the elongation in the atmosphere. did.

It is clear from FIG. 3 that excellent stress corrosion cracking resistance can be obtained when the Nb content exceeds 0.30%.

AC AQ ld is added as an effective deoxidizing agent, but if its content exceeds 1.0%, TCP phase tends to form, so the content of AA is set at 10% or less. .

C) N The Ni-based alloy of this invention is strengthened by adding N as an additive, but in this case, the N content is 0.050.
Solid solution strengthening becomes noticeable and work hardening ability improves to achieve high strength only when the content exceeds 0.25%.
If the N content exceeds 0.050 to 0.2, the precipitation of nitrides that deteriorate toughness etc. will become significant.
It was set at 5%.

In addition, Fig. 4 shows a Ni-based alloy in which the components other than N are kept almost constant among the components specified in this invention, and only N is changed, and the degree of cold working is constant at about 15 inches. Figure 5 is a graph showing the changes in strength (0.2% yield strength) and cutting edge properties when the same Ni-based alloy is changed in cold working degree, and the effect of N on work hardening properties is shown in Figure 5. This is a graph that confirms the effect.

From these Figures 4 and 5, it is clear that the N content is 0,050.
It can be seen that by adjusting the content to 0.25%, the alloy strength can be improved without significantly deteriorating the toughness.

S) Co, V, Ta, Zr, and Hf These components have the effect of improving the ductility and toughness of the alloy as well as improving the corrosion resistance, so one or more of these components may be included if necessary. The reason why the content ratio of each element is limited will be explained below along with the characteristic effects.

i) C.

The Co component is particularly effective in improving the hydrogen cracking resistance of the alloy, but if its content exceeds 5.0%, the TC
Since the P phase is likely to be generated, the Co content is 5.0.
Section below.

ii) V, Ta1Zr, and Hf These components are effective for stabilizing C, but if each is contained in an amount exceeding 1%, TCP phase is likely to be generated, so V, Ta, Zr, and Hf are The content of one or more of these was determined to be 1.0% or less.

C) Rare earth elements (RKM), Mf, Ca 1 and Y These components have the effect of improving the hot workability of the alloy by adding at least one kind of trace amount. The rare earth element content is 0.10%, the M2 content is 0.10%,
Ca content is 0.10% and Y content is 0.20
%, the rare earth element content is set at 0.10% or less, as low melting point compounds are likely to be formed and hot workability deteriorates. The content was determined to be 0.1% or less, the Ca content to be 0.10% or less, and the Y content to be 0.20% or less.

(n) Fe Since Fe has the effect of ensuring the strength of the alloy and reducing the Ni content to lower the price of the alloy, the remaining component was substantially made of Fe.

ri) Content balance of Cr, Mo, and W H2
Elution of N soil alloy in S -Co2- C6--8 environment (
Corrosion) is Cr, Ni, Mo, W, and C
Depends on u and Nb. That is, corrosion resistance is ensured by a surface film made of these elements, and the balance of content of these elements in this surface film is the most important factor in determining corrosion resistance. Mo is 10 times more effective than Cr against stress corrosion cracking in the above oil well environment, and W is 5 times more effective than Cr.
, Mo and W satisfy the formula 1 formula % respectively, Cr is 15 to 30%, Cu
is 0.30 to 3.0%, Nb is 0.30 to 3.0%,
If the Ni content is 45% or more, a corrosion-resistant film can be obtained that has excellent resistance to stress corrosion cracking even in an environment containing elemental sulfur (S).

In other words, the content balance of Cr, Mo and W is Cr
%) + 10 Mo (%) + 5W (%) (In the range of 140, H2S -Co2-Ct at about 250°C or less
-Sufficient corrosion resistance performance will not be exhibited in the S environment.

It should be noted that other elements such as B, an, Zn, and Pb do not have any adverse effect on the properties of the alloy of the present invention in trace amounts, so they should be contained as impurities at a concentration of 0.10% each.
It is permissible to exceed this upper limit, but care must be taken as exceeding this upper limit will have an adverse effect on workability and corrosion resistance.

Next, the present invention will be explained using examples and comparing with comparative examples.

〈Example〉' First, each alloy having the chemical composition shown in Table 1 is melted and then hot-worked into a plate material, which is cold-worked by about 20% to achieve the desired strength (room temperature To0 80-11ok2f/Tomo2) was obtained at .2% proof stress. From this board,
Each test piece to be subjected to a tensile test, an impact test, and a corrosion test was taken, and various tests were conducted in the following manner.

In addition, hydrogen cracking resistance test [The materials used were tested at 300℃ for 1
After performing a long-term heat treatment for 000 hours, a test piece was prepared.

(A) Tensile test test temperature: room temperature, test piece: 4.0mm φ, GL 20mm, (B) Charpy impact test test temperature: 0°C, test piece: 10mmX I Ommx 55)++m 2mmV notch (C) Stress corrosion cracking test Corrosion solution: 20% NaCA -19/lS -(0,
1,1,l O) atmH2S-2Q atm C
o2, test temperature: 250℃, immersion time: 50Q hr, additional window crab 1σy, test piece = 10 mm x 2 mm thickness x 75 mm length Ro, 2
With 5U notch (D) Hydrogen cracking resistance test NACE conditions: 5% NaCA -0.5%CH3
Co0H-1atm H2S.

Test temperature: 25℃, Soaking time is near 20 hours.

Addition resistance 1σy1 Test piece: 101m width x 2 thickness x 75mm length R0,25U
With notch.

The test results thus obtained are also shown in Table 1.

In addition, the results of the corrosion test are shown as "those in which no cracking or pitting corrosion was observed" and "x" in the test test where cracking or pitting corrosion occurred.

From the results shown in Table 1, it is clear that the alloy of the present invention exhibits excellent corrosion resistance even in a severe corrosive environment. It can be seen that none of the comparative alloys that deviate from the conditions exhibit sufficient corrosion resistance.

Overall effect> As explained above, according to the present invention, sulfur (E'
) is present as a single substance in a sour gas environment, it is possible to obtain a high-strength Ni-based alloy suitable for use in oil country tubular goods that has outstanding corrosion resistance, especially resistance to stress corrosion cracking and resistance to hydrogen cracking, making it extremely useful in industry. The effect can be obtained.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between P content and hydrogen cracking resistance (elongation in a corrosive solution/elongation in the atmosphere) in the alloy of the present invention. Figure 2 shows the S content in the alloy of the present invention. quantity and hot workability (
Figure 3 is a graph showing the relationship between Nb content and stress corrosion cracking resistance (elongation in corrosive solution/atmosphere) in an alloy having the same composition as the present invention except for Nb. Figure 4 shows the relationship between N content and strength (0.2% proof stress) and toughness in an alloy having the same composition as the present invention except for N. FIG. 5 is a graph showing the relationship between the degree of cold work and the strength ('0.2% proof stress), that is, the work hardening properties, in Ni-based alloys with various N contents. Chi 3 ζ ν 1 柕 (%) ] gu J'Pvnl supi/atmosphere raw... θ squeeze.

Claims (4)

[Claims] (1) C: 0.10% or less, Si: more than 0.05 to 0.30% by weight,
Mn: 2.0% or less, P: 0.030% or less, S: 0.
0050% or less, Ni: 45-60%, Cr: 15-3
0%, one or more of Mo and W: Mo is less than 16%, W is 5.0% or less, and the amount that satisfies 12≦Mo (%) + 1/2 W (%) < 16, Cu: 0.30 to 3.0%, Ti: 0.050% or less,
Nb: 0.30-3.0%, Al: 1.0% or less, N:
More than 0.050 to 0.25% Fe and other unavoidable impurities: Consists of the remainder, and is characterized by having a component composition that satisfies the formula: Cr (%) + 10 Mo (%) + 5 W (%) ≧ 140 and
High strength Ni with excellent stress corrosion cracking resistance and hydrogen cracking resistance
Base alloy. (2) In terms of weight percentage, C: 0.10% or less, Si: more than 0.05 to 0.30%,
Mn: 2.0% or less, P: 0.030% or less, S: 0.
0050% or less, Ni: 45-60%, Cr: 15-3
0%, one or more of Mo and W: Mo is less than 16%, W is 5.0% or less, and the amount that satisfies 12≦Mo (%) + 1/2 W (%) < 16, Cu: 0.30 to 3.0%, Ti: 0.050% or less,
Nb: 0.30-3.0%, Al: 1.0% or less, N:
Contains more than 0.050 to 0.25%, and further contains one or more of Co: 5.0% or less, V, Ta, Zr, and Hf: 1.0% or less each, Fe and other unavoidable impurities: The composition is characterized by being composed of the remainder and having a composition satisfying the following formula: Cr (%) + 10 Mo (%) + 5 W (%) ≧ 140,
High strength Ni with excellent stress corrosion cracking resistance and hydrogen cracking resistance
Base alloy. (3) In terms of weight percentage, C: 0.10% or less, Si: more than 0.05 to 0.30%,
Mn: 2.0% or less, P: 0.030% or less, S: 0.
0050% or less, Ni: 45-60%, Cr: 15-3
0%, one or more of Mo and W: Mo is less than 16%, W is 5.0% or less, and the amount that satisfies 12≦Mo (%) + 1/2 W (%) < 16, Cu: 0.30 to 3.0%, Ti: 0.050% or less,
Nb: 0.30-3.0%, Al: 1.0% or less, N:
Contains more than 0.050 to 0.25%, and further contains rare earth elements: 0.10% or less, Mg: 0.10% or less, Ca: 0.10% or less, Y: 0.20% or less, Fe and other unavoidable impurities: Fe and other unavoidable impurities. ,
High strength Ni with excellent stress corrosion cracking resistance and hydrogen cracking resistance
Base alloy. (4) In terms of weight percentage, C: 0.10% or less, Si: more than 0.05 to 0.30%,
Mn: 2.0% or less, P: 0.030% or less, S: 0.
0050% or less, Ni: 45-60%, Cr: 15-3
0%, one or more of Mo and W: Mo is less than 16%, W is 5.0% or less, and the amount that satisfies 12≦Mo (%) + 1/2 W (%) < 16, Cu: 0.30 to 3.0%, Ti: 0.050% or less,
Nb: 0.30-3.0%, Al: 1.0% or less, N:
more than 0.050 to 0.25%, and further contains Co: 5.0% or less, one or more of V, Ta, Zr, and Hf: each 1.0% or less, and rare earth elements. : 0.10% or less, Mg: 0.10% or less, Ca: 0.10% or less, Y: 0.20% or less, Fe and other unavoidable impurities: the remainder Cr (%) + 10 Mo (%) + 5 W (%) ≧ 140.
High strength Ni with excellent stress corrosion cracking resistance and hydrogen cracking resistance
Base alloy.