JPS58199851A - High nickel alloy for acidic oil well - Google Patents

Abstract

PURPOSE:To obtain the titled high Ni alloy superior to a conventional similar steel to be compared in mechanical properties and much superior to the steel in corrosion resistance, by prescribing the contents of C, N, Si, Mn, Ni, Cr, Mo and (C+3Mo) except the balance Fe. CONSTITUTION:This high Ni alloy for an acidic oil well consists of, by weight, <=0.05% C, <=0.04% N, <=1.0% Si, <=1.0% Mn, 35-45% Ni, 20-30% Cr, 4-7% Mo, (Cr+3Mo)>=40% and the balance Fe with inevitable impurities. The high Ni alloy has superior corrosion resistance in environment contg. chloride, CO2 and H2S, and it is an economical alloy as the material of a pipe for an acidic oil well. A significant effect is shown on crevice corrosion by especially prescribing the content of (Cr+3Mo) to said value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to high nickel alloys for acid well applications.

Recently, with the depletion of oil resources, deep oil wells and acid oil wells, which had been abandoned until now, have been reconsidered. However, these oil wells are exposed to large amounts of chloride, CO2 and H.
Carbon steel and low-alloy steel, which have been conventionally used as materials for oil country tubular goods, cannot withstand use because they often contain 2S and are highly corrosive, so high-alloy materials with excellent corrosion resistance are required.

Examples of such high alloy materials that are actually used or proposed for oil country tubing include 13Cri martensitic stainless steel, austenite and ferrite duplex stainless steel, austenitic high nickel alloy, and nickel-based alloys, cobalt-based alloys, titanium alloys, etc. Among these, 13Cr-based martensitic stainless steels and duplex stainless steels are resistant to corrosion due to CO2, but when l-1 and 8 coexist, they are susceptible to sulfide stress corrosion. Cracking (
It has the disadvantage of easily causing SSCC>, and cannot be applied to harsh oil well environments with high H and S contents.

Nickel-based alloys, cobalt-based alloys, and titanium-based alloys are resistant to corrosion in environment F containing chlorides, CO2, H, and S, but they also contain large amounts of expensive materials such as Ni, Mo, Co, and TI. It has the disadvantage of being used for.

Therefore, as pipe material for acidic oil wells, chloride, CO2,1
A high nickel alloy, which has excellent corrosion resistance and is economical in combination with 1 and S, was devised.

Among the properties required for materials for oil country tubular goods in acidic oil wells, the following four properties are particularly important.

(1) Stress corrosion cracking (SSCC) should not occur in the CI-Co2-82S environment.

(2) Resistant to cracking under conditions of contact with carbon steel in c+-CO2-H2s environment F.

(3) Resistant to localized corrosion such as crevice corrosion and pitting corrosion in a CI-Co2-H2S environment.

(4) Have high mechanical strength.

Among these four characteristics, mechanical strength (4) can be solved by cold-opening in high nickel alloys, but (1) and (2) in this cold-opening state are
What is important is whether the properties of , and (3) can be ensured.

Therefore, the present inventor used the method (1) of immersing a U-bend test piece in a boiling solution of high concentration MgCl2 as a reagent for accelerating the stress corrosion cracking phenomenon. However, high concentration MgCl
Although tests using two solutions are said to have many problems in accelerating the chloride stress corrosion cracking phenomenon in a neutral environment, we thought it would be suitable for simulating an environment such as an acidic oil well.

Furthermore, in order to evaluate the susceptibility to hydrogen embrittlement in (2), the present inventors applied 5% NaCl saturated with T-12S at room temperature with a carbon steel flat plate in contact with the
-0.5%C) (, COOH aqueous solution.This is because hydrogen is generated on the surface of the U-bending test piece due to electrochemical action caused by contact between different metals.C+-C02
- This is because hydrogen embrittlement sensitivity in an H2S environment can be properly evaluated.

Further, in the same sense, the present inventor used a method of immersion in an aqueous solution of 10% FcCl, .6H20 as the accelerating reagent in (3). This was based on the fact that this solution was acidic.

The effects of the alloy materials studied based on the results of the accelerated tests of type :) in a c+7-co2=n,s environment were confirmed.

That is, after melting and casting various Ni-Cr-Mo alloys shown in Table 1 using a Hatake wave furnace, hot forging, hot rolling,
A test piece was prepared through cold rolling.

Regarding this Ni-Cr-Mo alloy test piece,
Boiling 35% M in CI2 solution and boiling 42% Mgc
Chloride stress corrosion cracking tests were conducted in +2 solution. FIG. 1 shows the results of the test plotted against N1 and MO content. As shown in Fig. 1, Ni and Mo
A synergistic effect is observed. This means that 42% MgCl
Approximately 45% or more of N1 has been required to prevent stress corrosion cracking in two solutions, but as shown in Figure 1, stress corrosion cracking occurs when Ni content is less than 45% due to the synergistic effect with Mo. I found out that it doesn't. In FIG. 1, 0 indicates that no stress corrosion cracking occurs, and . indicates that stress corrosion cracking occurs.

Next, for the same material shown in Table 1, Cl-Co2-H
The susceptibility to hydrogen embrittlement in a 2S environment was evaluated. Figure 2 shows the results plotted against the Ni and Fe contents. As shown in Figure 2, the Ni content is approximately 5
If it exceeds 0%, the sensitivity to hydrogen embrittlement becomes extremely high. In Figure 2, ○ indicates those that did not undergo hydrogen embrittlement;
・ indicates that it has undergone hydrogen embrittlement.

;.

Furthermore, for the same materials shown in Table 1, 35°C and 70°C
Figure 3 shows the result of a crevice corrosion test conducted in a 10% To''cc13'6H20 solution at 10°C.

From this figure 3, the content of Cr+3kjo (%) is about 4
It can be seen that the amount of corrosion decreases rapidly after reaching 0%. It has been known that increasing Cr and Mo is effective in improving crevice corrosion resistance. The fact that it is effective against corrosion is a completely new finding of the present invention. In Fig. 3, ○ indicates a test at 35°C1 (soil 70°C).

As explained in Section 1-1, the present invention was made in view of the conventional problems as a material for acidic oil wells, and based on three findings as a result of research by the inventor. A suitable high nickel alloy is provided.

The high nickel alloy for acidic oil wells according to the present invention includes (1) C6
0.05%, N≦0.04%, SI≦ ], 0%, MnS
2.0%, Ni: (5-45%, Cr20-30%, M
Contains o4-7%, Cr + 3 Mo≧4
The first invention is a high nickel alloy for acidic oil wells, characterized in that the balance is 0% Fe and unavoidable impurities,
(2) C60.05%, N≦0.04%, SiS2.0
%, to111≦1.0%, N135-45%, Cr20
-30%, Mo4-7%, and Cu53%, TiS2
．． Contains one or more selected from 5%, Nb≦1.5%, ■≦1.5%, Ga, Cr+3Mo
A second invention is a Nokel alloy, a material for acidic oil wells, characterized in that the balance is Fe ≧40% and unavoidable impurities, (3) C60.05%, N≦0.04%, SiS
2.0%, M n≦1.0%, N135-45%, Cr
20-30%, N'Io4-7%, AI≦0.5%, and the balance is Fe and unavoidable impurities with Cr+3Mo≧40%. (4) C60.05%, N
≦0.04%, SiS2.0%, MnS2.0%, Ni
35-45%, Cr20-30%, tMo4-
7%, Cu53%, TiS2.5%, Nb≦1.
5%, ■≦1.5% of the selected one or two
species or more, further contains AI≦0.5%, and Cr
+3 Remaining Fe where Mo≧40% and ■; avoidable 1
This invention consists of four inventions, with the fourth invention being a high nickel alloy for acidic oil wells, characterized in that it is made of a pure substance.

The high nickel alloy for acidic oil wells according to the present invention will be explained in detail.

First, the components and component ratios of the high nickel alloy for acidic oil wells according to the present invention will be explained.

C is 8! In terms of mechanical strength, the more the better, but 0.05%
If the C content exceeds 0.2%, carbides will precipitate at grain boundaries and cause intergranular corrosion. Therefore, the C content should be 0.05% or less.

N has the effect of increasing strength and improving crevice corrosion resistance, but in high Ni-containing alloys, if it is contained in an amount exceeding 0.04%, it causes intergranular corrosion and deteriorates workability.

Therefore, the N content is set to 0.04% or less.

Sl and Mn are those used as deoxidizing agents in steelmaking. If both Si and Mn are contained in excess of 1%, workability and toughness will be impaired. Therefore, the content of Si and Mn should be 1% or less.

Ni is an element that is effective against stress corrosion cracking, especially Mo
However, if the Mo content is less than 35%, no effect on stress corrosion cracking can be expected even if the specified amount of Mo is contained. This is also clear from what is shown in FIG. On the other hand, Ni has the effect of increasing susceptibility to hydrogen embrittlement,
As shown in FIG. 2, when the content exceeds about 50%, significant embrittlement occurs. Therefore, in view of safety, it is desirable to limit the Ni content to 45% or less. Therefore, Ni
The content is 35-45%.

C" exhibits an excellent effect on crevice corrosion due to its synergistic effect with Mo, and when the Cr content is in the range of 20 to 30% and the added content with Mo is 40% or more. As shown in Fig. 3, the crevice corrosion decreases rapidly.From this, the Cr content is set to 20 to 30%.

As mentioned above, Mo is effective against stress corrosion cracking and crevice corrosion.
It exhibits excellent effects due to its synergistic effect with Ni and Cr, and while balancing the contents of both N1 and Cr,
From what is shown in Figures 1 and 3, Mo-containing mice are 4 to 7
%.

Cu, ]'1, and Nb, ~' are all included to improve corrosion resistance. In other words, C'u is an element that is particularly effective in improving crevice corrosion resistance, and is included depending on oil well conditions, but if it is included in excess of 3%, the effect is saturated and This seriously impedes hot workability. Therefore, the Cu content is set to 3% or less. Also, TI, Nb,
\l is effective in preventing intergranular corrosion as a strong carbide-forming element, and at the same time increases mechanical strength through precipitation hardening of fine carbides, so can it be included depending on oil well conditions?1. If the content exceeds 5%, processability will be significantly hindered. Therefore, the contents of Ti, Nb, and V are 1.
5% or less.

A1 is an element that improves the workability of the alloy as a strong deoxidizing agent, but if the content exceeds 0.5%, the workability deteriorates. Therefore, the A1 content is set to 0.5% or less.

Next, examples of high nickel alloys for acidic oil wells according to the present invention will be described together with comparative examples.

EXAMPLES Test specimens were produced by melting and casting using a normal melting method so that the components and proportions shown in Table 2 were obtained, and then processed. Table 3 shows mechanical properties, stress corrosion cracking,
The test results for crevice corrosion are also shown.

As is clear from Table 3, the high nickel alloy for acidic oil wells according to the present invention has inferior mechanical properties compared to comparative steels, and moreover, its corrosion resistance is significantly superior to all comparative steels. It is something that

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between MO content and Ni content. Figure 2 is a graph showing the relationship between Fc content and Ni content. This is a graph showing 2. Procedural amendment (voluntary) 1. Indication of the case 1982 Patent Application No. () 82689 2, Title of invention: High Nickel Alloy for Acid Oil Wells 3, Person making the amendment Relationship with the case Patent Applicant address: Wakihama-cho, Chuo-ku, Kobe + T H3-18 Name
(]]9) Kobe Steel, Ltd. Representative Takashi
Hashi-tei, Da 4, Agent, Address: 9 o 1', Yumifutowa Toyocho Co-op, 2-2-15 Minamisuna, Koto-ku, Tokyo; Address: 136 Telephone (646) 6 ]', No. 15, Correction Order Lft. 1 (Voluntary) 6. Subject of amendment: Full text of the amended specification 7. Contents of the amendment As shown in the appendix Specification page 1. Name of the invention: High nickel alloy for acidic oil wells 2. Scope of claims (+) CS2.05wL%, N'- (1,04
u+L%, SiS; IJ11111%, MnS2.0w
1%, Ni35-4.5u+L%, Cr2+1-30u
+t%, ~'Io 4-7wL%, Ga, Cr
13Mo≧40Ill[%, the remainder I゛(・and T'
LT1: A high nickel alloy for acidic oil wells, characterized by being made of a blunt material. (2) CS2.05u+L%, N≦0.04u+t%,
SiS1.0wt%, MnS2. Ou+t%, Ni 3
5-45ullt%, Cr2 (1-30wL%, Mo4
-7u+t% and -qu+-3upj,%,
Ga, Cr +3 Mo≧40u+L%, the remainder 1
A high nickel alloy for acidic oil wells, characterized by consisting of impurities. (3) CS2.051111%, N≦0.04iuL%
, 5iS1.0iut%, Mn≦], 0IIIt%, N
i 35-45iut%, Cr2O-30u+t%, M
o 4-7u+t%, -ICu I Z3w, p and A
Contains I≦0.5wt%, Cr+3Mo≧40
A high nickel alloy for use in acidic oil wells, characterized in that it consists of a balance Fc of u+'t% and a 10% impurity. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high nickel alloy for use in acidic oil wells. Recently, deep oil wells and acid oil wells, which had been abandoned until 2009 due to the depletion of 4i oil resources, have been reconsidered. However, these oil wells contain large amounts of chloride, CO2 and l
! , S are often included, and the corrosion resistance is extremely severe, and the carbon steel and cast alloy steel conventionally used as materials for oil country tubular goods cannot withstand use, and high alloy materials with excellent corrosion resistance are required. In addition, materials that are actually used or proposed for oil country tubing include 1, '+Ci martensitic stainless steel, duplex stainless steel of austenite and 7-elite, and austenitic high-grade stainless steel. There are nickel alloys, nickel-based alloys, cobalt alloys, titanium alloys, etc., but among these, are 13C-based martensitic stainless steels and duplex stainless steels resistant to corrosion by CO7? 11. It has the disadvantage of easily causing sulfide stress corrosion cracking (SSCC) when H2S coexists, and cannot be applied to harsh oil well environments where H2S content is high. In addition, nickel-based alloys, cobalt-based alloys, and titanium-based alloys are resistant to corrosion in environments containing chlorides, CO2, and +12S, but they use large amounts of expensive materials such as Ni, Mo, Co, and T1. There is a difficulty in doing so. Therefore, chloride, CO2, H
An alloy with excellent corrosion resistance and economical properties in coexistence with 2S, that is, a high nickel alloy was devised. Among the properties required for materials for oil country tubular goods in acidic oil wells, the following four properties are particularly important. (+) CI--Do not cause stress corrosion cracking (sscc) in a Co2-H2S environment. (2) Resistant to cracking (HE) under conditions of contact with carbon steel in a CI--Co2-H2S environment. (3) Resistant to localized corrosion such as crevice corrosion and pitting corrosion in a CI--Co, -H2S environment. (4) Have high mechanical strength. Among these four characteristics, mechanical strength (4) can be solved by cold working in high nickel alloys, but (1) and (2) in this cold working state
What is important is whether properties (3) and (3) can be ensured. Therefore, the present inventor used a method of immersing an L1 bending test piece in a boiling solution of high concentration MgC+2 as an accelerated test for stress corrosion cracking phenomenon (1). However, high concentration Mti
Although tests using CI and solutions are said to have many problems in accelerating the chloride stress corrosion cracking phenomenon in a neutral environment, we thought it would be suitable for simulating environments such as acidic oil wells. . Furthermore, in order to evaluate the susceptibility to hydrogen embrittlement in (2), the present inventors tested 5% NaCl saturated with H2S at room temperature with a carbon steel flat plate in contact with the above U-bending test piece.
A test was conducted in which the sample was immersed in a 11.5% CH1COOFI aqueous solution. This is because hydrogen is generated on the surface of the U-bending specimen due to electrochemical action caused by contact between different metals, and C1--
This is because hydrogen embrittlement susceptibility in a CO2-H2S environment can be properly evaluated. Further, in the same sense, the present inventor used a method of immersion in a 10% FeCL 6 )+20(F) aqueous solution as the accelerated test (3). This was based on the fact that this solution was acidic. The effects of the alloy materials studied based on the results of these three types of accelerated tests in a CI--Co2-142S environment were confirmed. That is, various Ni Cr Mo alloys shown in Table 1 were melted and cast using a high-frequency furnace, and then subjected to hot-opening silver making, hot rolling, and cold-opening rolling to create test pieces. Then, this Ni-Cr-Mo alloy test piece was tested in boiling 35% MgCI□ solution and in boiling 42% MgCI□ solution.
Figure 1 shows that a chloride stress corrosion cracking test was carried out in a CI2 solution, and the results were calculated for a NikMo content of 1''.As shown in Figure 1, ni, N
Synergistic young fruits of I and Mo are observed. This means that 42%
Approximately 45u+t to prevent stress corrosion cracking in MgCl2 solution
% or more, but as shown in Figure II, it was discovered that stress corrosion cracking does not occur when the Ni content is 45 wL% or less due to the synergistic effect with P-jo. In FIG. 1, ◯ indicates that no stress corrosion cracking occurs, and ◯ indicates that stress corrosion cracking occurs. Next, regarding the same materials shown in Table 1, CI″″-Co
The susceptibility to hydrogen embrittlement in a 2-H2S environment was evaluated. FIG. 2 shows the results plotted against the Ni and Fe contents. As shown in FIG. 2, when the Ni content exceeds about 50 uL%, the susceptibility to hydrogen embrittlement increases significantly. In FIG. 2, ◯ indicates that the sample did not undergo hydrogen embrittlement, and ◯ indicates that it did undergo hydrogen embrittlement. Furthermore, for the same materials shown in Table 1, 35°C and 70°C
Figure 3 shows the result of a crevice corrosion test in a 10% FeCL+ .6H20 solution at . From this figure 3, the Cr+3Mo (%) content is about 40u.
It can be seen that the amount of corrosion rapidly decreases after reaching +t%. Therefore, an increase in Cr and Mo contributes to crevice corrosion resistance.
It was known that L was effective, but a specific content of C
It is a completely new finding of the present inventor that a specific addition ratio of C and Mo is effective for this crevice corrosion. This is test C. As explained above, the present invention was made in view of the conventional problems as a material for acidic oil wells, and was made based on three findings as a result of research by the present inventor. The present invention provides a high nickel alloy suitable as a material for acid oil wells.The high nickel/kel alloy for acid oil wells according to the present invention has (1.)C
60,05IIIt%, N≦0.04u+t%, Si
≦1. OuL%, MnS2.0wt%, Ni 35-4
5IIIt%, Cr2O-30u+t%, Mo 4-7
An invention of 1JA1 is a high-Ninkel alloy for acidic oil wells, which is characterized by containing Cr13Mo≧40u+L%, with the remainder being F'e and unavoidable impurities.
(2) C≦O, 05wt%, N≦0.04wt%,
Si≦1. OuL%, MnS2, 0wt%, Ni 35
-45u+t%, Cr 2020-3O%, Mo4-7
u+t%, Cu 1-3u+L%, and Cr
A high-Ninkel alloy for acidic oil wells, characterized in that the balance is composed of +3Mo≧40w[%, and the remainder is do + and unavoidable impurities, is also the second invention.
u+t%, S1≦1.0w1%, MnS2. OuL%,
Ni 35-45iuL%, Cr2O-30uL%,
Mo4-7u+t%, Cul-3iuL% and A1≦0
．． Contains 5u+L% and Cr+3M. The third high ink alloy for acidic oil wells is characterized in that the balance is Fe of ≧40 iut% and unavoidable impurities.
This invention consists of three inventions. The high nickel alloy for acidic oil wells according to the present invention will be explained in detail. First, the components and component ratios of the high-grade Kickel alloy for acidic oil wells according to the present invention will be explained. From the viewpoint of mechanical strength, the more C, the better. However, O, (15
If the content exceeds wt%, Cr carbide will precipitate at grain boundaries, causing intergranular corrosion. Therefore, the C content is 0.05w
t% or less. N has the effect of increasing strength and improving crevice corrosion resistance, but in high N1-containing alloys, if the content exceeds 0.04 ulL%, it causes intergranular corrosion and deteriorates workability. . Therefore, the N content is set to 0.04u+t% or less. Sl and Mn are used as deoxidizers in steel manufacturing, and if both contain more than 1w1%, workability and toughness will be impaired. Therefore, the Sl and Mn contents are set to be equal to or higher than Lout%. N1 is an element that is effective against stress corrosion cracking, especially Mo
However, if the content is less than 35wL%, even if the content is less than 35wL%. Even if it is contained in a specified amount, no effect on stress corrosion cracking can be expected. This is clear from what is shown in FIG. On the other hand, Ni has the effect of increasing the sensitivity to hydrogen embrittlement, and as shown in No. 2M, when its content exceeds about 50 w[%], a remarkable embrittlement phenomenon occurs. Therefore, in view of safety, it is desirable to limit the Ni content to 451% or less. Therefore, the N content is 35 to 45 ψt%.
shall be. Due to the synergistic effect of Cr with MO, 1. It shows an excellent effect on gap vI5 corrosion, and the Cr content is in the range of 20 to 30 wt%, and the added content with 3N40 is 40 u.
As shown in FIG. 3, the crevice corrosion decreases rapidly above +t%. From this, the Cr content is 2O-30u
+L%. As mentioned in -, Mo shows an excellent effect on stress w4 corrosion cracking and crevice corrosion l due to its synergistic effect with N1 and Cr. From what is shown in Figures 1 and 3, Mo-containing wrinkles are 4
~7u+L%. Cu is included to improve corrosion resistance (see below),
Cu is an element that is particularly effective in increasing crevice corrosion resistance, and is included depending on the oil well conditions.
If it is less than 3%, the effect of improving corrosion resistance will be weak.
If the content exceeds u+t%, the effect will be saturated and hot workability will be significantly inhibited. Therefore, the Cu content is set to 1 to 3u+L%. A1 is an element that improves the workability of the alloy as a strong deoxidizing agent, but if the content exceeds 0.5u+t%, the workability deteriorates. Therefore, the AI content is Q, 5wt%
The following shall apply. Next, examples of high nickel alloys for acidic oil wells according to the present invention will be described together with comparative examples. EXAMPLES Test specimens were produced by melting and casting using a normal melting method so that the ingredients and proportions shown in Table 2 were obtained, and then processed. Table 3 shows the test results for mechanical properties, stress corrosion cracking, and crevice corrosion. As is clear from Table 3, the high nickel alloy for acidic oil wells according to the present invention has poorer mechanical properties than the comparative steels, and moreover, its corrosion resistance is far superior to all comparative steels. It is excellent. 4. Brief explanation of the drawings Figure 1 is a graph showing the relationship between Mo content and N1 content, Figure 2 is a graph showing the relationship between Fe content and Ni content, and Figure 3 is Cr+3Mo content. It is a graph showing the relationship between and superposition loss.

Claims (4)

[Claims] (1) C50.05%, N 60.04%, S1≦1.
0%, MnS2.0%, Ni3545%, Cr20-
30%, Mo 4-7%, and Cr+3Mo
A high nickel alloy for acidic oil wells, characterized in that the balance Fe is ≧40% and the balance is unavoidably dull. (2) C50.05%, N≦0.04%, SI≦1.0
%, MnS2.0%, Ni3545%, Cr20-30
%, Mo4-7 Ayu, and Cu63%, TiS2.5
%, NbS2.5%, \'≦1.5%, or 2 or more types selected from ``-''-, Doka, Cr+3M
A high nickel alloy for acidic oil wells, characterized in that the balance F'e is o≧40%, and a: avoidable impurities. (3) C50.05%, N≦0.04%, SiS2.0
%, MnS2.0%, Ni3545%, Cr20-30
%, Mo4-7%, AI≦0.5%, and C
A high nickel alloy for acidic oil wells, characterized in that the remainder is Fe and unavoidable impurities, with r+3Mo≧40%. (4) C50.05%, N≦0.04%, SiS2.0
%, MnS2.0%, N135-45%, Cr20-
30%, Mo4-7%, and Cu63%, TiS2.
5%, NbS2.5%, and one or more selected from ■≦1.5%, and further contains AI≦0.5%, and Cr + 3Mo≧40%. Remainder Fe
and unavoidable impurities.