JPS58199852A - High nickel alloy for acidic oil well - Google Patents

Abstract

PURPOSE:To obtain the titled alloy superior to a 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, >=1 kinds among Ti, etc., and (Cu+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%, >=1 kinds among 0.6-1.5% Ti, 0.6-1.5% Nb and 0.6- 1.5% V, and the balance Fe with inevitable impurities. The crevice corrosion resistance of the alloy is remarkably enhanced by prescribing the content of (Cr+ 3Mo) in the composition as mentioned above.

Description

[Detailed description of the invention] The present invention relates to high nickel alloys for acid well applications.

Recently, with the depletion of petroleum resources, deep oil wells and acid oil wells, which had been abandoned until 2010, have been put into the ground. However, these wells contain large amounts of chloride, CO2 and
Carbon steel and low-alloy steel, which have been conventionally used as materials for oil country tubular goods, cannot withstand use due to their extremely corrosive properties in many cases, and 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 13Cr-based martensitic stainless steel, austenitic and ferrite dual-phase stainless steel, austenitic high-nickel alloy, There are nickel-based alloys, cobalt-based alloys, titanium alloys, etc. Among these, 13Crt% martensitic stainless steel and duplex stainless steel are resistant to corrosion due to CO2, but when H and S 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 a high H2S content.

Nickel-based alloys, cobalt-based alloys, and titanium-based alloys are resistant to corrosion in environments containing chlorides, CO2, H, and S, but they also contain large amounts of expensive materials such as Ni, Mo, Co, and T1. It has the disadvantage of being used for.

Therefore, chloride, C02, 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.

(1) Stress corrosion cracking (SSCC) should not occur in a CI--Co2-H2S environment.

(2) Resistant to cracking (IIE) under conditions of contact with carbon steel in a CI--Co2-H2S environment.

(Button CI--Resistant to localized corrosion such as crevice corrosion and pitting corrosion in a Co2-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 in this cold thin soil state, (1), ( What is important is whether properties 2) and (3) can be ensured.

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

Furthermore, in order to evaluate the susceptibility to hydrogen embrittlement in (2), the present inventors tested 5% Na
A test was conducted in which the sample was immersed in a 1-0.5% CH3CO0H 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 CI''-C
This is because the sensitivity to hydrogen embrittlement in an O2-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% FeCl=.6H20 as the accelerated test (3). This was based on the fact that this solution was acidic.

Then, the effects of the alloy materials studied based on the results of these three types of accelerated tests in a CI"--Co?-H2S environment were confirmed.

That is, various Ni-Cr-Mo alloys shown in Table 1 are melted and cast using a high frequency furnace, followed by hot forging, hot rolling,
A test piece was prepared through cold rolling.

Regarding this Ni-Cr-Mo alloy test piece,
Boiling 35% MgCl2 solution and boiling 42% Mg
Chloride stress corrosion cracking tests were conducted in Cl2 solution.

FIG. 1 shows the results of the test plotted against the Ni and Mo contents. As shown in FIG. 1, synergistic young fruits of Ni and Mo are observed. This means that 42%Mg
Approximately 45 wt% to prevent stress corrosion cracking in CI 2 solution
Although the above amount of Ni has been required, as shown in Fig. 1, it has been found that stress corrosion cracking does not occur when the Ni content is 45u+t% or less due to the synergistic effect with Mo.

In FIG. 1, ◯ indicates that no stress corrosion cracking occurs, and ◯ indicates that stress corrosion cracking occurs.

Next, for the same materials shown in Table 1, CI”-CO
, -H2S environment was evaluated for susceptibility to hydrogen embrittlement. FIG. 2 shows the results plotted against N1 and Fe content. As shown in FIG. 2, when the N1 content exceeds about 50 u+t%, the susceptibility to hydrogen embrittlement increases significantly. In the second cabinet, ○ indicates that the material was not subjected to hydrogen embrittlement, and . indicates that it was subjected to hydrogen embrittlement.

Furthermore, the same materials shown in Table 1 were subjected to crevice corrosion tests in 10% FeC11' 6H:0 solutions at 5°C and 70°C and summarized in Figure 3.

From this figure 3, the Cr+3Mo (%) content is approximately 4r1
It can be seen that the number of corrosive rats rapidly decreases after the wt% limit. It has been known that increasing Cr and Mo is effective in improving crevice corrosion resistance, but
In r and Mo, the fact that a specific sugar addition ratio of C and Mo is effective for this crevice corrosion property is a completely new finding of the present inventor.・Ha7(
1'c test.

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

The high nickel alloy for acidic oil wells according to the present invention has (1) C
60,05u+L%, I≦(1,04u+1%, S1
≦1.0u+L%, MnS2. Ou+L%, Ni 35
-45u+L%, Cr2(1-30u+L%, Mo4
-7wL% and '[i 0.6-1,5u+t%, Nb
0.6-4.5++ut%, \'0.6-1.5wL
The first method is to provide a high nickel alloy for acidic oil wells, which is characterized by containing one or more of the following: Cr+Mo≧40%, with the balance being Fe and unavoidable impurities. As an invention, (2) C60,05u+t%, N
≦0.04u+t%, S■≦1.0w1%, MnS2.
0+lIL%, N135~45u+L%, C"20~3
0u+L%, Mo 4-7wt%, Cu≦3u+t% and 'l'i 0.6-1.5u+t%, Nb O, 6~
1. Cr+3M
A high nickel alloy for acidic oil wells characterized by consisting of o≧40 u+t%, balance F”e and unavoidable impurities, is also defined as a second invention, (3) C60,05ul%, N≦
0.04u+L%, Si'1.0iut%, N1n 1
．． Ou+L%, Ni 35-45iut%, Cr2O-
30u+L%, Mo 4-7uL%, A1≦0. Fou
1% and T i O,6-1,5u+1. %, Nll0
16-1.5 wL%, ＼; Contains one or more selected from 0.6-1.5+u1%, and 0 [
・+: Remaining Fe and f where No. λ1o≧40u+L%;
A third invention is a high nickel alloy for acidic oil wells characterized by comprising an avoidable 1ζ pure substance, (4) C60,05
u+t%, N≦0.04+++L%, Si≦1.0+u
t%, MnS2.0wt%, Ni 35-45u+t
%, Cr 2O-30u+1%, Mo 4-7wL%,
From the four inventions of which the fourth invention is a high nickel alloy for acidic oil wells, which is characterized by containing Cu63w1%, AI≦0.5+uL%, and Cr+3Mo≧4011rt%, the balance being Fe and unavoidable impurities. It is what it is.

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 llI! In terms of mechanical strength, the more the better, but 0,0
If the C content exceeds 511 It%, carbides will precipitate at grain boundaries and cause intergranular corrosion. Therefore, the C content will be 0.
05u+t% 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 excess of 0.04u+t%, it causes intergranular corrosion and deteriorates the workability. Therefore, the N content is set to 0.04 ul% or less.

Si and Mn are those used as deoxidizing agents in steel manufacturing, and if both Si and Mn are contained in an amount exceeding 1 wt%, workability and toughness will be impaired. Therefore, Sl, Mn
The content shall be 1 ust% or less.

Ni is an element that is effective against stress corrosion cracking, especially Mo
However, if the content is less than 35u+t%, no effect on stress corrosion cracking can be expected even if a specified amount of MO is contained. This is clear from what is shown in FIG. On the other hand, Ni has the effect of increasing susceptibility to hydrogen embrittlement, and as shown in FIG. 2, when its content exceeds about 50 wt%, a remarkable embrittlement phenomenon occurs. Therefore, in view of safety, it is desirable to limit the Ni content to 45u+t% or less. Therefore, the N1 content is set to 35 to 45 Illt%.

Cr shows an excellent effect on crevice corrosion due to its synergistic effect with Mo, and the Cr content is in the range of 20 to 30 w [%, and the added content of 3 to 10 is 40 ul [%].
As shown in Fig. 3, the crevice corrosion suddenly decreased in the case of -. From this, the Cr content is 20.~30u+
Let it be L%.

As mentioned above, Mo is effective against stress corrosion cracking and crevice corrosion.
It shows excellent effects due to its synergistic effect with Ni and Cr, and from the balance with the content of both Ni and Cr,
From what is shown in Figures 1 and 3, the Mo content is 4 to 7.
Let it be u+L%.

Cu is included to improve corrosion resistance, and C
u is an element particularly effective in increasing crevice corrosion resistance,
It is contained depending on the oil well conditions, but the content is 3 iut.
If the content exceeds %, the effect will be saturated and hot workability will be severely impaired. Therefore, the Cu content is 3u+L%
The following shall apply.

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 set to 1°0.5 wt% or less.

T'i, Nb, and V are all elements that aim to improve corrosion resistance and mechanical strength. In other words, T1, Nb, and V are effective in preventing intergranular corrosion as strong carbide-forming elements. Also, TI, Nb,
The mechanical strength increases due to the solid solution strengthening of (2), so it can be included depending on the oil well strip 1'H, but 0.6++
If the content is less than +L%, these effects cannot be expected, and if the content is 1.5u+t%, the processability will be significantly inhibited. Therefore, the contents of TI, Nb, and V are each 0.
．． The content should be 6 to 1.5 wt%.

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 prepared by melting and casting using a conventional melting method so that the components and proportions shown in Table 2 were obtained. Table 3 shows W1 mechanical properties, stress corrosion cracking,
The test results for crevice corrosion are also shown.

As is clear from Table 3 of 2, the high nickel alloy for acidic oil wells according to the present invention has superior mechanical properties compared to comparative steels, and its L corrosion resistance is significantly higher than that of all comparative steels. It is excellent.

[Brief explanation of 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 a graph showing the relationship between Cr+3Mo content and weight loss. This is a graph showing. Procedural amendment (voluntary) June 21, 1980 Kazuo Wakasugi, Commissioner of the Japan Patent Office1, Indication of the case 1982 Patent Commissioner No. 2257062, Name of the invention High nickel alloy for acidic oil wells3, Person making the amendment Case Relationship with Patent Client Address 1-3-18 Wakihama-cho, Chuo-ku, Kobe Name (1
19) Kobe Steel, Ltd. Representative Takahashi
Takayoshi 4, agent 1 No. 5, 901 Hoop, Fujiwa Toyo-cho, 2-2-15 Minamisuna, Koto-ku, Tokyo Date of amendment order (voluntary) 6. A of the invention increased by amendment (None) 7, Subject of amendment (1) List of documents attached to the application (2) Figure 1, Figure 2, Figure 3 8, Contents of amendment As per attached sheet 1 Figure ■ Do 1 \ 1 ko” No, 91 Tsuba゛ ・) 1 sho No, BOX
O ” NO・7 ＼No、5su40＠＜）0 Φ＼IJo、6shi
ゝ－〜〜 ・Tou Q, 4 ・NO, 3 ・ ・tJo, 2 No, 1 Ha , , , ,
l,. Brass 2 No. 11 oN. , 1゜ ○

Claims (4)

[Claims] (1) C', 0.05wL%, N≦0.04ut
%, S; ≦1. Ou+t%, for≦1.0uIt%, Ni
35-45wt%, Cr2O-30u+t%, Mo4
-7u+t% and T i O,6-1,5'iut%,
Nb O, 6-1,5wt%,\'0.6-1,5w
A high nickel alloy for acidic oil wells, characterized in that it contains one or more selected t% of Nauchikara, and consists of Cr13Mo≧40w[%, the balance being Fe and unavoidable impurities. (2) C60.05uL%, N <, 0.04u
rL%, SiS2.011%, Mn≦1.011%, N
i 35-45u+t%, Cr20-. 30u+t%,
Mo4-7u+t%, Cu≦3wt% and Ti0.6-
1.5uut%, NbO, 61.5u+t%, VO
, 6-1.5 wt%, and the balance is Fe and unavoidable impurities with Cr+3M'o≧40u+t%. Nickel alloy. (3) C60,05u+t%, N≦0,04u+L%
, SiS 2,011%, Mn 1. OWL%, Ni 3
5-45Illt%, Cr2O-30wt%, Mo4-
7wt%, A1≦0,5u+L% and T10.6-1.
5wt%, NbO, 6~1.51%, VO, 6~
Contains one or more selected from 1.5wt%, and the remainder is Fe, with Cr+3Mo≧40u+t%
and A: A high nickel alloy for acidic oil wells, characterized by comprising avoidable impurities. (4) C60,05u+t%, N≦0.04u+t%
, Si≦+, 0u+t%, Mn≦1. Out%, Ni
35-45u+L%, Cr2O-30wt%, Mo4
-7wt%, Cu≦3u+t%, AI≦0.5wt% and TiO,6~l, 5u+t%, NbO,6-1,
A high nickel alloy for acidic oil wells, characterized in that it contains 5u+t%, VO, 6-1.5wt%, and the balance is Fe and inevitable impurities such that Cr+3Mo≧40u+t%.