JPS58210155A - High-strength alloy for oil well pipe with superior corrosion resistance - Google Patents

Abstract

PURPOSE:To obtain a high-strength alloy for an oil well pipe with stress corrosion cracking resistance and superior corrosion resistance, by specifying a composition consisting of C, Si, Mn, P, S, sol.Al, Cr, Ni, N, Mo, W, Fe, etc. and the relation among the components. CONSTITUTION:This alloy consists of, by weight, <=0.1% C, <=1.0% Si, 3.0- 15.0% Mn, <=0.030% P, <=0.010% S, <=0.5% sol.Al, 18.0-22.5% Cr, 15.0-40.0% Ni, 0.1-0.4% N, <=4.0% Mo and/or <=8.0% W, and the balance Fe with inevitable impurities while satisfying 1/2Mn%+Ni%>=18% and Cr%+Mo%+1/2W%= 1.5-4.0%. To the alloy may be added restricted amounts of Co, Cu, rare earth elements, Y, Mg, Ca, Ti, etc.

Description

[Detailed Description of the Invention] This invention has high strength and excellent corrosion resistance, especially excellent stress corrosion cracking resistance, and is suitable for oil and natural gas mining under severe conditions where these characteristics are required. The present invention relates to seven alloys suitable for use in oil country tubular goods.

In recent years, there has been a marked trend toward deeper oil and natural gas wells, and in addition, wet hydrogen sulfide (H2) is present in the oil and gas produced.
Increasingly, corrosive components such as carbon dioxide (CO2) and chlorine ions (CA'') are included.

As the well depth increases in this way, the pressure of the crude oil and gas produced, as well as the soil strength of the stratum, also increases, and the tensile load due to the own weight of the oil country tubular goods used also increases. The oil country tubular goods used for this are
Not only is high strength required to withstand these forces, but also H2S, CO2, and CA! - & Oil and gas well environments containing corrosive components (hereinafter referred to as
Since stress corrosion cracking is the main cause of corrosion under (referred to as t-C1-oil well environment), it is required to have excellent stress corrosion cracking resistance.

On the other hand, a common method for preventing corrosion of oil country tubular goods is to inject a corrosion inhibitor called an inhibitor into the oil country tubular goods, but this method is not effective when oil and gas wells are located offshore. It is often not possible to utilize it, and sufficient results cannot be expected. Furthermore, a method of coating oil country tubular goods with a protective film may be used, but in this case as well, sufficient corrosion prevention results cannot be expected.

In view of these circumstances, 1. Recently, stainless steel has been introduced, as well as Incoloy and 71 Steroid (all product names).
Attempts have been made to use high-grade materials such as Incoloy and Hastelloy in the manufacture of oil country tubular goods, but these materials, especially Incoloy and Hastelloy, are expensive because they both contain large amounts of expensive Ni. None of the materials meet the standard 5-C.
ot-C1-The details of corrosion behavior in an oil well environment have not yet been fully elucidated, and furthermore, it does not have the high strength required for oil country tubular goods for deep wells. Therefore, the present invention From the above-mentioned viewpoints, these companies have developed high strength and excellent stress corrosion resistance that can withstand oil and natural gas extraction in deep wells and harsh corrosive environments, especially in H2S-Cα-C1 oil well environments. As a result of research to obtain materials for oil country tubular goods with breakability, (a) Ht S -Cα-
C1 - The main type of corrosion in an oil well environment is stress corrosion cracking, but the behavior of stress corrosion cracking in this case is completely different from that of general stress corrosion cracking in austenitic stainless steel. In other words, whereas general stress corrosion cracking is deeply related to the presence of C1-, in Ht S -CCh -CI- oil well environment, not only C1- but also &S is affected. is large.

(c) Ph5- Steel pipes used for practical use as oil country tubular goods are generally subjected to cold working to improve their strength, but cold working significantly reduces the resistance to stress corrosion cracking mentioned above.0 (c) Ph5- The elution rate (corrosion rate) of steel in a CO2-C11 oil well environment depends on the contents of iron, Cr, Ni, iron, and W. Corrosion resistance is maintained by a surface film made of these components, and these Mo (%) also increases its resistance to stress corrosion cracking.
) + TW (Season: 1.5 to 4.0-1, and
Mn: 3.0-15.0 To, Cr: 18.
Contains 0 to 22.5 inches, Ni: 15.0 to 40.0 degrees, furthermore Mo: 4.0 To or less and W: S.
If one or two of the following are contained in
- (J- HtS-CO under oil well environment, especially below 150℃
z -C7-A surface coating exhibiting excellent resistance to stress corrosion cracking in an oil well environment is obtained.

(d) The Ni component not only has an effect on the surface film, but also has an effect on improving stress corrosion cracking resistance structurally.

(e) When 0.1 to 0.4% of N is contained as an alloy component, the alloy strength is further improved.

(f) When 0.05 to 3.0 grams of CO is included as an alloy component, the alloy is further solid solution strengthened and work strengthened, and the stress corrosion cracking resistance is also improved.

<g> Including 0.05 to 3.0% of Cu as an alloy component further improves the strength and corrosion resistance of the alloy.

(h) Rare earth elements as alloy components, particularly preferably one or two of the rare earth elements with an atomic number of 57 to 71.
Species or higher (hereinafter collectively referred to as rare earth elements):
0.001-0.10 inch, Y: 0.001-0.
20%, Mg: 0.001~0.10'1r1
Ca: 0.001-0.10chi, and Ti: 0.0
When one or two of the above 05% to 050% is contained, the hot workability of the alloy is further improved.

The findings shown in (a) to 01) above were obtained.

Therefore, this invention was made based on the above findings, and includes: C: 0.1% or less, Si: 1.0% or less, Mn: 3.0-15°Ol, P: 0.030%. Below, S: 0.010'% or less, son, 7M! :
0.5 inch or less, Cr: 18.0 to 22.5 inch, Ni
: 15.0~40.0chi, N: 0°1~0.4%
Contains Mo: 4.0916 or less and W:S,
0
5-3.0%, rare earth elements: 0.001-0.10
Chi, Y: 0.001-0.20 chi, Mg: 0-00
1-0.10%, Ca: 0.001-0-10%,
and Ti: o, oos to 0.50 Ti, and Mo (%) + TW (1): 1.5 to 4.0.
%, satisfies 1-: The remainder is Fe and other unavoidable impurities (weight %), and the alloy is characterized by a high-strength alloy for oil country tubular goods having excellent stress corrosion cracking resistance.

Next, the reason why the composition range of the alloy of the present invention is limited to the above-mentioned range will be explained.

(a) CC If the C component exceeds 0.1%, stress corrosion cracking tends to occur at grain boundaries, so the upper limit of its content was set at 0.1%.

5i Si component is a necessary component as a deoxidizing component, but if its content exceeds 1.0%, hot workability and ductility will deteriorate, so the upper limit value is set to 1.0%. 0 (c) Kn Kite component, as mentioned above, improves stress corrosion cracking resistance in coexistence with Ni, Cr, Mo, and W.
It has the effect of promoting strength improvement by cold working and further promoting the solid solution of N, but if the content is less than 3.0%, the desired effect cannot be obtained; Since hot workability deteriorates if the content exceeds the content, the content was set at 3.0 to 15.01.

(d) P The P component has the effect of increasing the susceptibility to stress corrosion cracking, and this effect becomes significant when the content exceeds 0.030-. Therefore, the upper limit value has been set to 9.030- %.

(e) SS The S component has the effect of deteriorating the hot workability of the alloy, and this effect tends to become noticeable when its content exceeds 0.010%. Therefore, the upper limit of its content The value was set at 0.010%.

(f) 5o11. kl AA' is an effective component as a deoxidizing component similar to Si, and the upper limit of its content is set because it does not impair the alloy properties even if it is included up to 0.5% soA and AA content. is set at 0.5% for SO4 All (g) Cr The Cr component has the effect of significantly improving stress corrosion cracking resistance in coexistence with Iori, Ni, Mo, and W components; If the content is less than 18.0%, the desired excellent stress corrosion cracking resistance cannot be secured;
&5-Co2-
In the C/- oil well environment, no further improvement effect appears;
Moreover, since hot workability may be deteriorated in some cases, the content is determined to be 18.0 to 22.5%.

(h) Ni The Ni component improves the stress corrosion cracking resistance of the alloy, but if its content is less than 15.01, the desired excellent stress corrosion cracking resistance cannot be ensured. In addition, hot workability may be deteriorated from the viewpoint of the structure, and on the other hand, 40.
Since even if the content exceeds 0%, no further improvement effect on stress corrosion cracking resistance will appear, so the content was set at 15.0 to 40.0%, taking economic efficiency into consideration. .

(i) N The N component improves the alloy structure and is dissolved in the base material.
It has the effect of strengthening this, but its content is 0.1'%
If it is less than 0.4, the desired effect cannot be obtained;
%, it becomes difficult to melt the alloy and form ingots, so the content was set at 0.1 to 0.4%.

(j) Mo and W As mentioned above, these components include Mo, Cr, and Ni.
There is a uniform effect of improving stress corrosion cracking resistance in coexistence with Mo: 4.0% and W: &0%.
Since no further improvement effect will be seen in the ot-cz-oil well environment, the content should be reduced in consideration of economic efficiency.
: 4-0% or less, and w:s, o* or less, respectively.

The Co component is required to have these characteristics because it does not simply dissolve into the base material and strengthen it, but also promotes work strengthening and improves the stress corrosion cracking resistance of the alloy. However, if the content is less than 596, the desired effect of improving the above action cannot be obtained. However, since Co is expensive, in consideration of economic efficiency, the content is was set at 0.05 to 3.01.

(If) Cu The Cu component has the effect of improving the strength and corrosion resistance of the alloy, so it is included as necessary when these properties are particularly required, but if the content is less than 0.051, The desired improvement effect did not appear in the above action; on the other hand, 3.0
Since the hot workability of the alloy will deteriorate if the content exceeds
It was determined that

- Rare earth elements, Y, ceramics, Ca, and Ti These components have the effect of improving hot workability, so they should be included when hot working is required under particularly severe conditions. However, the content of rare earth elements: 0.0
Less than 0.011, Y2 less than 0.0011, Mg: 0.00
less than 1 mo, Ca: less than α001-, and Ti: 0.
If the content is less than 0.005%, the desired hot workability improvement effect cannot be obtained; on the other hand, rare earth element = 0.101, Y: 0.209I
If the content exceeds I1Mg: 0.1%, Ca: 0.10%, and Ti: 0.50%, a tendency for deterioration will appear in the hot workability improvement effect. The content of rare earth elements: 0.001-0.10%, Y: 0.00
1-0.20 嗟, Mg: 0.001-0.10*, C
a: 0.001-0.1091y, and Ti:
It was set at 0.005 to 0.50 inches.

l w < h) Figure 1 shows the test results under a severe corrosive environment, that is, H2S-cot.
-cz- Regarding stress corrosion cracking resistance under an environment equivalent to an oil well environment, Cr (%) + MO (%) + 2
It shows the relationship between W (%) and -7Mn (%) 10Ni (*).

That is, Fe-Mn-Cr-Ni-Mo system with various contents of Cr, Ni, Mo, and W;
Fe-Mn-Cr-Ni-W system, and Fe-Mn
- Cr-Ni-Mo-W alloy is melted, cast, forged and hot-rolled to form a hot-rolled plate with a thickness of 12cm,
Next, this hot-rolled sheet was subjected to solution treatment by holding it at a temperature of 1075°C for 30 minutes and cooling with water, and then, for the purpose of improving strength,
Processing rate: 25 inches of cold working, and from the resulting cold-rolled plate, perpendicular to the rolling direction, thickness: 2 mm x width: 10 mm
A test piece with a length of X near 5 m+ was cut out, and a tensile stress corresponding to the yield strength (0.2% proof stress) was applied to the test piece S using the three-point support beam jig shown in Figure 2. With the addition of FI2s at a pressure of 5 atm, c
A stress corrosion cracking test was conducted by immersing the specimen in a 5 4 NaC solution (temperature: 150'C) saturated with O2 at a pressure of 10 atm for 960 hours, and after the test, the presence or absence of cracking in the test piece was observed.

(1) When plotted in relation to 10Mo(%l+TW(chi)), the results shown in Figure 1 regarding stress corrosion cracking were shown.In Figure 1,
○ marks indicate no cracks, and X marks indicate cracks. TMn below the result shown in FIG.
It is clear that the desired stress corrosion cracking resistance cannot be obtained when the value of (%) +Ni (%) is less than 18 inches. From the above results, in order to ensure excellent stress corrosion cracking resistance, Cr (%) +M.

(1) +-! -w (%): 2056 or more, -!
-Mn (*) +Ni (%): 2 Must be 18 or more.

Regarding the content of Mo and W, MO(qb) + 2 W
It is specified in (%) that the atomic weight of W is approximately 2
If this value is less than 1.5%, the desired stress corrosion cracking resistance cannot be secured; on the other hand, if this value is less than 4.0% Even if Mo and W are contained in amounts exceeding the above, the effect of further improving stress corrosion cracking resistance will not appear as described above, and the content of W will be substantially unnecessary, resulting in increased costs. Since this is not economical, the value of MO (qb) + TW (%) was set at 1.5 to 4.0.

In addition, in the alloy steel of this invention, B-Sn, Pbs, and Zn are each 0 as other avoidable impurities.
- Even if the content is in the range of 0.05 mm or less, the properties of the alloy of the present invention will not be impaired.

In addition, when manufacturing the alloy steel oil country tubular goods of the present invention, first a normal electric furnace, an argon-oxygen decarburization furnace (AOD)
A molten kettle having a predetermined composition is melted using an electroslag melting furnace (ESR furnace), weight: 2
After pouring into a steel ingot of approximately 1,000 ton, it is soaked at a temperature of 1,050 to 1,250°C and then bloomed into a billet with a diameter of 150 to 300 mmφ. However, in order to add strength, it is made into a pipe material by hot working under conditions such that the wall thickness reduction rate is 30 inches or more in a temperature range of 1000 degrees Celsius or less, where recrystallization does not proceed. The process is preferred.

The resulting tubing can be either as-hot-worked or
After solution treatment at a temperature of 850 to 1150°C,
Furthermore, wall thickness reduction rate: 5 to 70 inches, preferably 10 to 50 inches
The pipe material in this state is put into practical use after being subjected to 2-column processing, but the yield strength of the pipe material in this state is 0.2 mm yield strength) = 70 kgf/
It has a strength higher than that of satin, and has excellent ductility and toughness as well as stress corrosion cracking resistance.

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

In each example, molten steel having the composition shown in Table 1 was prepared by a normal melting method, and then 10 pieces of steel ingots were prepared.
After soaking at a temperature of 50 to 1200°C, hot forging was performed to obtain a billet. At this time, it was observed whether or not cracks occurred in the billet for the purpose of evaluating hot workability. The billet is then milled, heated to a temperature of 1,050 to 1,200°C, and subjected to hot extrusion processing to form a tube material.Furthermore, for the purpose of imparting strength and strength to this tube material, it is heated to a temperature of 1050 to 1200 ° C. After solution treatment at a temperature of 1,050 to 1,125°C, cold drawing was performed at the wall thickness remaining ratio shown in Table 1 to obtain an outer diameter of 60.3 mmφ x wall thickness of 51 [1 m]. Comparative alloy tube materials 1 to 10 and conventional alloy tube materials 1 to 4 were manufactured, respectively.

In addition, Comparative Alloy Tube Materials 1 to 10 all have a configuration in which the content of one of the constituent components or the conditional expression (indicated with a square mark in Table 1) is outside the scope of the present invention. Also, the conventional alloy tube material 1 is 5US316,
The conventional alloy tube material 2 has a composition corresponding to SUS 310S, the conventional alloy tube material 3 to SUS 329J1, and the conventional alloy tube material 4 to Incoloy 800.

Next, the length: 20 m was obtained from the various pipe materials obtained as a result.
A test piece of m is cut out, and a portion corresponding to a central angle of 60° is cut along the length of the test piece. Pass through the pipe bolt and tighten with a nut to create a yield strength of 0 on the outer surface of the pipe.
．． A tensile stress equivalent to 2% proof stress) was applied, and to the test piece S in this state, &S was added at 0.1 atm, 1 atm, and 10 atm, respectively, and C) was added at 10 atm in each case. A stress corrosion cracking test was carried out by immersion in a 51 NaCJ solution (liquid temperature: 150° C.) containing 311OHtS-Cot for 960 hours, and the presence or absence of stress corrosion cracking after the test was observed. These results are shown in Table 2, along with the presence or absence of cracking during hot forging, yield strength (0.2 yield strength), and elongation. In Table 2, the O marks indicate cases where no cracks have occurred, and the X marks indicate cases where cracks have occurred.

From the results shown in Table 2, comparative alloy tube materials 1 to 10 are as follows:
In contrast, the alloy tube materials 1 to 30 of the present invention all have high strength, high ductility, and poor properties in at least one of hot workability, stress corrosion cracking resistance, and strength. It has excellent hot workability and stress corrosion cracking resistance, and is suitable for particularly severe corrosion conditions of 10 atmospheres + 42! (-1
There was no cracking even in 0 atm C (32-54 NaC6 solution), and it is clear that the material has even better properties than conventional alloy pipe materials 1 to 4, which have relatively poor stress corrosion cracking resistance. be.

As mentioned above, the alloy of the present invention has particularly high strength and excellent stress corrosion cracking resistance, so it can be used in oil and natural gas extraction in harsh environments where these properties are required. It exhibits extremely excellent performance when used as oil country tubular goods and geothermal country tubular goods.

[Brief explanation of drawings]

(%) +Ni (*) and Cr (%) +M+1 (%
) A diagram showing the relationship with 10'W (%), a vX2 diagram, and FIG. 3 are front views showing aspects of stress corrosion cracking tests using plate-shaped and tubular test pieces, respectively. Applicant: Sumitomo Metal Industries, Ltd.

Claims (1)

[Claims] +l) C: 0.1% or less, St: 1.0
% or less, Mn: 3. (J ~ 15.0%, P: (1,0
30 inches or less, S: 0.010 inches or less, go/, Ag:
0.5% or less, Cr: 18.0-22.5chi, N
i: 15.0~40.0ch, N: 0.1~0.
4th inch south, Mo: 4.0% 1゛ branch and W: S
, contains 144 or 2 of 0% or less, and
Cr (%) +Mo (%) -1-”W (%)
: 204 or more, Mo (%) + 2 W (%)
: High strength for oil country tubular goods with excellent corrosion resistance, characterized by having a composition satisfying 1.5 to 4.0% 1, with the remainder consisting of F'e and other unavoidable impurities. alloy. 12) C: 0.1% or less, Si: 1-0
'%% or less Mn: 3.0-15.0chi, P: Sail 030chi1], S: 0. +110%, below PL, sat
, Ad: 0.5% or less, C, r: ] 8.0
~22.5chi, Ni: l 5.0~40.0%, N
: 11.1 to 0.4%, one or two of Mo: 4-04 or less and w: 8.0% or less
Contains seeds, further contains Co:0.05-3.0, and. Cr (%) +Mo (season + TW (1: 204
Above, M・)(chi)+-HW(chi): 1.5 to 4.
0%. 1. A high-strength alloy for oil country tubular goods having excellent corrosion resistance, which satisfies the above requirements and has a composition with the remainder consisting of Fe and other unavoidable impurities. (3) C: 0.1% or less, St: 1.0% or less, Mn: 3.0 to 15.0%, P: 30% or more, S: 0.010% or less, sol? , Ali! :
0.5% or less, Cr: 18.0-22.5chi, N
i: 15.0-40.0%, N: oa1-0.4%
17, containing one or two of Mo: 4.0% or less and W: 8.0% or less, and Cu: 0.
05 to 3.0%, and 2 Mn (%) + Ni ('%): 184 or more, M
o ('1) Kashi-, 1V (Sword: 1.5
A high-strength alloy for oil country tubular goods having excellent corrosion resistance, characterized in that it has a composition (the above weight %) consisting of i14 of ~4.0 taro and the remainder consisting of Ii'e and other unavoidable impurities. 1/11 C: 0.1% or less, Si: 1.0% or less, Mn: 3. (1-15.0%, P: 0.0
301 or less, S: 0.010% or less, soe, A
l: 0.5% or less, Cr: 18.0-22.
5s, Ni: 15.0-40.0 To, N:
Contains 0.1 to 0.4 Lt-, Mo: 4.0% or less, and W: 8. Contains one or two of Q% or less, and further contains rare earth elements: 0.001 to 0.10%, Y
: 0.001~0.20chi, Mg: 0.001~0.
10%, Ca: 0.001-0.10ch, and '
17i: Contains one or more of 0.005 to 0.50, and TN'In (%) +N
t (%) = 18% or more, Mo, (%) + 2 W
(%): 1.5 to 4.0%, with the remainder consisting of Fe and other unavoidable impurities (the above type Il
A high-strength alloy for oil country tubular goods having excellent corrosion resistance. (5) C: 0.1% or less, Si: 1.0% or less, Mn: 3.0 to 15.0%, P: 0.030 or less, S: 0.010 or less, soA! , AJ:
0.5% or less, Cr: 18.0-22.5chi,
Ni: 15.0~40.0chi, N: 0.1~0.4%
Contains one or two of Mo: 4-0% or less and W:Q, 0% or less, and further Co: 0
．． 05-3. Ol and Cu: 0. -05~3.0
1+ and Mo (%) + 2 W (%
): 1.5 to 4.0%, and has a composition (weight tIb) with the remainder consisting of Fe and other unavoidable impurities. (6) C: 0.1% or less, Si: 1-Q% or less, Mn: 3.0-15.0%, p: o, o a o
%% or less S: 0.010 or less, txol, AI
: 0.5% or less, Or: 18.0 to 22.5 inches, Ni: 15.0 to 40.0 inches, N: 0.1 to 0.4 inches, Mo: 4-096 or less, and W: S, O*%
Contains one or two of the following, and further contains Co:
0.05-3.0% and rare earth elements: 0.001-0
．． i 0%, Y: 0.001-0.20%, big:
0.1) 01~0.10chi, Ca: 0.001~
0.10%, and 1 or 2' or more of ri: 00115 to 0.50%, W with L6, and HMn (%) + Ni (%): 181 or more, Mo
(%) +TW (%): 1.5 to 4.0%, (add 14, and the remainder consists of Fe and other unavoidable impurities. High strength alloy for oil country tubular goods. (7) 'C: o, t S Lu lower, Si: 1.0
% or less, Pi'in: 3.0-15.0%, P:
0.030% or less, S:0010 or less, sob, A
d: 0.5'ir or less, Cr: 18.0~2
2.5chi, Ni: 5.0-40.0%, N:
Contains 0.1 to 0.4%, one type or 2f of Mo: 4.0% or less and W: 8.0% or less
ii, further containing Cu: 0.05 to 3.0%,
Rare earth elements: o, o o i ~ o, to%. Y: 0.001-0.20%, Mg: 0.001
~0. tOchi, Ca: 0.001-0.10%,
and Ti: '0.005 to 0.50%, and Mo 0%) +-! -w (%): 1.5~4
A high-strength alloy for oil country tubular goods having excellent corrosion resistance, which satisfies Q96 and has a composition (the above weight %) consisting of Fe and other unavoidable impurities. tdl C: 0.1 fo or less, Si: 1. Q% or less, Mn: LO ~ 15.0chi, P: '0.030chi or less, S: 0.010- or less, so4) J: 0.5
96 or less, Cr: 18.0-22.5chi, Ni: 1
Contains 5.0-40.01 N: 0.1-0.4%, Mo: 4-0'it or less and W: 8.0%
Contains one or two of the following, and further Co:0
．． 05-3.0%, Cu: o, o 5-3.0
Chi and rare earth elements: 0.001 to 0.10 Chi, Y: 0
．． 001~0.20chi, Mg: 0.001~0.10
to, Ca: 0.001~O-10嗟,'' and T
i: 1 type from 0.005 to 0.50%, then 2
``Mn (%) + Ni (%): 18% or more, 1 Mo (%) + TW (%): 1.5 to 4.0
%, with the remainder consisting of Fi'e and other unavoidable impurities.