JPS5811735A - Production of high-strength oil well pipe of superior stress corrosion cracking resistance - Google Patents

Abstract

PURPOSE:To improve the strength and stress corrosion cracking resistance of an oil well pipe in the stage of producing the oil well pipe of Ni-Cr stainless steel contg. specific metallic elements by regulating the contents of Cr, Mo, W in a specific range. CONSTITUTION:The Ni-Cr stainless steel of such compsn. that contains <0.05% C, <1.0% Si, <2.0% Mn, <0.030% P, <0.005% S, <0.5% sol.Al, 35-60% Ni, 22.5-35% Cr and 1 or 2 kinds of <4% Mo and <8% W, and satisfies the two equations expressed by the equation[I]between the contents of Cr, Mo, W is hot worked to a pipe material at >=10% thickness reduction ratio at <=1,000 deg.C and at >=800 deg.C finishing temp. Such pipe material is cold-worked at 10-60% thickness reduction ratio and is used in deep wells or heavily corrosive environment, whereby the oil well pipe of superior strength and stress corrosion cracking resistance for oil wells and natural gas wells is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing high-strength oil country tubular goods having excellent stress corrosion cracking resistance.

In recent years, due to the deterioration of the energy situation, there has been a marked tendency for oil and natural gas wells to become deeper;
Some deep wells with a depth of 10,000m or more have appeared.

Furthermore, due to similar circumstances, it is becoming increasingly difficult to extract oil and natural gas in a harsh corrosive environment containing humid hydrogen sulfide, as well as corrosive components such as carbon dioxide gas and chloride ions.

As oil and natural gas are drilled in such harsh environments, the oil country tubular goods used therein are required to have high strength and excellent corrosion resistance, especially resistance to stress corrosion cracking. .

As a general countermeasure against corrosion of oil country tubular goods, it is known to introduce a corrosion inhibitor called an inhibitor, but this method is often not effective in applications such as offshore oil wells.

From this point of view, consideration has recently begun to be given to the use of high-grade corrosion-resistant high-alloy steels such as stainless steel and Incoloy and Hastelloy (all trade names) for the production of oil country tubular goods. H2S
The details of the corrosion behavior of -Co, -(, L-) in oil well environments have not yet been fully elucidated, and at present they do not have the high strength required for oil country tubular goods for deep wells. be.

Therefore, from the above-mentioned viewpoint, the present inventors have developed a material with high strength and excellent durability that can withstand oil drilling in deep wells and severe corrosive environments, especially in H,S-Co2-at- oil well environments. As a result of research to manufacture oil country tubular goods with stress corrosion cracking resistance, (a) HzS -C02-C1-1! The main type of corrosion in the stainless steel is stress corrosion cracking, but the behavior of stress corrosion cracking in this case is completely different from that of general austenitic stainless steel. That is, while general stress corrosion cracking is deeply related to the presence of at-, in the oil well environment mentioned above, the influence of H and S is greater than that of aZ-.

(b) Steel pipes used for practical use as oil country tubular goods are generally:
Cold working is performed to improve strength, but cold working significantly reduces the resistance to stress corrosion cracking.

(c) The elution rate (corrosion rate) of steel in a H2S -CO2- (31- environment depends on the contents of Or, Ni5Mo, and W, and corrosion resistance is maintained by the surface film made of these components, and These components also increase its resistance to stress corrosion cracking, and in particular, MO is 1-0 times more effective than Or, and Mo is twice as effective as W. W is Or (%)
+10 Mo @+5 W (%)≧50chi.

1.5%≦MO(%) +-W(%)<4%.

While satisfying the conditional expression, the Ni content should be 35 to 60%.
, when the Or content is 22.5 to 35%, H2S -ao2- is extremely corrosive even in cold-worked materials.
It is possible to obtain a surface coating that exhibits excellent resistance to stress corrosion cracking under an oil well environment, particularly in a harsh environment of 150° C. or lower.

(→ Regarding N1, it has the effect of increasing stress corrosion cracking resistance not only on the surface film but also on the structure.

(e) When N is contained as an alloy component in the range of 0.05 to 0.3%, the strength of the tube material is further improved.

(f) S content as an unavoidable impurity is set to 0.000
If the temperature is reduced to 7- or less, the hot workability of the tube material will be significantly improved.

(ω) When the P content as an unavoidable impurity is reduced to 0.003 or less, the hydrogen cracking susceptibility decreases significantly.

(h) When O is included as an alloy component at 2% or less, corrosion resistance is further improved.

(1) As alloy components, rare earth elements: 0.10% or less, Y: 0.20% or less, Mg: 0.10% or less, T
By containing one or more of the following: 1:0.5% or less and Oa: 0.10% or less, hot workability is further improved.

(J) However, in order to ensure the desired high strength, first add 105 cl to 1250 cl to the alloy having the above composition.
Hot working at a temperature of 1000°C or less with a wall thickness reduction rate of 10% or more and a finishing temperature of 800°C or more, with intermetallic compounds and carbides completely dissolved in the solid solution by heating to a temperature within the temperature range of 100°C. By applying this process, the crystal grains are made finer without the precipitation of intermetallic compounds and carbides that cause corrosion resistance deterioration, and the formation of these fine grains gives the pipe material high strength and toughness. If it is made of a material, it is necessary to subsequently perform cold working at a wall thickness reduction rate of 10 to 60 inches to strengthen it.

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

Therefore, this invention was made based on the above findings, and it is preferable that O: 0.05% or less, Sl: 1.0% or less, Mn: 2.0% or less, P: 0.030% or less. is P: 0.0 for the purpose of further improving hydrogen cracking resistance.
0.03% or less, S: 0.005'% or less.

Desirably, for the purpose of further improving hot workability, S:o,
ooo 7% or less r soL, fiJ! , : 0.5
% or less, N1: 35-60%, Or: 22.5-3
5%, contains one or two of MO: less than 4% and W: less than 8%, and further contains N as necessary.
: 0.05 to 0.3%, Cu: 2% or less, Co: 2% or less, rare earth elements: 0.10 or less, Y: 0.20 or less, Mg: 0.10% or less, Ti: 0 .5% or less,
and Ca: 0.10 - Contains one or more of the following, with the remainder consisting of Fe and unavoidable impurities (the above weight %, below all expressions in ``chi'' mean weight %) , and Or (%) + 10 Mo 1%) + 5 W(
%) ≧50chi.

1.5%≦Mo &1)-1--W(a)<4%.

An alloy that satisfies the following conditions is hot worked at a wall thickness reduction rate of 10% or more at 1000°C or less and a finishing temperature of 28oO°C or more, and then cooled at a wall thickness reduction rate of 10 to 60 inches. This method is characterized by a method for manufacturing high-strength oil country tubular goods with excellent stress corrosion cracking resistance by performing preliminary processing.

Next, the reason why the component composition and hot and cold working conditions are limited to the above-mentioned conditions in the method of the present invention will be explained.

A. Ingredient composition (a) The lower the O C content, the more suppressed the precipitation of carbides, so the heating temperature during hot working can be lowered, and this increases the strength after cold working. It works effectively. Therefore, it is desirable that the C content be as low as possible, but if the C content exceeds 0.05%,
Since intergranular stress corrosion cracking is likely to occur, the upper limit was set at 0.05%.

(b) 5i Sl is a necessary component as a deoxidizing component, but if its content exceeds 1.0%, hot workability will deteriorate, so its upper limit is set at 1.0%. Established.

(c) Mn The Mn component tends to have a deoxidizing effect like Sl, and since this component has little effect on stress corrosion cracking resistance, the upper limit value was set at a relatively high 2.0%. Ta.

(d) P The P component as an unavoidable impurity has a content of 0.0
If it exceeds 30%, the effect of increasing stress corrosion cracking susceptibility appears, so it is necessary to set the upper limit at 0.030% to keep stress corrosion cracking susceptibility to a low state. Also, P
It has been found that as the content is reduced, hydrogen cracking resistance rapidly improves after reaching 0.003%, and from this point of view, particularly excellent hydrogen cracking resistance is required. In this case, it is desirable that the P content be 0.0030% or less.

(e) S The S component as an unavoidable impurity has a content of 0.0
If it exceeds 0.05%, it has the effect of deteriorating hot workability, so it is necessary to set the upper limit at 0.005% to prevent deterioration of hot workability. In this way, the S component has the effect of deteriorating hot workability when its content increases, but when its content is lowered to 7% O,0O0, hot workability is further improved. ,! Therefore, if hot working under severe conditions is required, it is desirable to set the S content to 0.0007% or less.

(f) ybM is effective as a deoxidizing component like Sl and blood,
Since it does not impair the characteristics of the pipe material even if the content is up to 0.5% in terms of 5oLAfi7 content, the content was determined to be 0.5% or less in terms of soL and AI content.

←) Ni The N1 component has the effect of improving the stress corrosion cracking resistance of pipe materials, but if its content is less than 35%, the desired excellent stress corrosion cracking resistance cannot be secured;
Even if the content exceeds 100%, no further improvement effect on stress corrosion cracking resistance appears, so the content was increased to 35 to 60%, taking economic efficiency into consideration.

(b) It is a component that significantly improves stress corrosion cracking resistance when coexisting with the 0r Or acid component, Ni', Mo, and W components, but even if its content is less than 22.54, hot workability is improved. However, in order to secure the desired stress corrosion cracking resistance, the content of Mo and W must be increased accordingly, which is economically disadvantageous. Therefore, the lower limit was set at 22.5%. On the other hand, if the S content exceeds 35%, deterioration in hot workability cannot be avoided no matter how much the S content is reduced, so the upper limit was set at 3511b.

(i) Mo and W As mentioned above, these components have an equal effect of improving stress corrosion cracking resistance when coexisting with Ni and Or, but Mo: 49% or more and W: 8% or more, respectively. % or more, if the environmental temperature is below 150℃
In a corrosive environment of Co and -OL-, no further improvement effect was observed, and in consideration of economic efficiency, the respective contents were determined to be less than 4% for Mo and less than 8% for W. Also, M.O.
Regarding the content of and W, the conditional expression: Mo(91il+
The reason for specifying W@ is that the atomic weight of W is approximately twice that of MO, and the effects are approximately equal at -.If this value is less than 1.5%, the above-mentioned adverse effects will occur, especially at temperatures below 150°C. The desired stress corrosion cracking resistance could not be obtained under the environmental conditions, and on the other hand, this value was
Even if the above-mentioned insufficient and substantially unnecessary amount of Mo
and W, which is not economical, and from this point of view,
The value of Mo(a)+−WS) was set at 1.5 to less than 4 h.

(j) N Since the N component has the effect of improving strength through solid solution strengthening, it is included as necessary when particularly high strength is required, but if the content is less than 0.05%, the desired strength cannot be achieved. No improvement effect can be obtained, and on the other hand, if the content exceeds 0.3%, melting and ingot making become difficult, so the content was set at 0.05 to 0.3%.

(k) Ou and CO These components have a uniform effect of improving the corrosion resistance of the pipe material, and CO also has a solid solution strengthening effect.
It is included as necessary, especially when even better corrosion resistance is required, but if Cu exceeds 2 qb, hot workability will deteriorate, while CO can be contained even if it exceeds 2 qb. Since no further improvement effect was observed, the upper limits were set at 2% for Cu and 2% for Co, respectively.

(t) Rare earth elements, Y, Mg, TL and C
a These components have a uniform effect of further improving hot workability, so they are included as necessary when hot working is performed under severe conditions. Rare earth elements: 0.10 %, Y: 0.20%.

Mg: 0.10%, Ti: 0.5%, and Ca:
Even if the rare earth element content exceeds 0.10%, no improvement effect on hot workability is observed, and even deterioration phenomenon appears.
% or less, Y: 0.20% or less, Mg: 0.10%
Below, Ti: 0.5% or less, and Ca: 0.
It was set at 10% or less.

(m) Or(%) +1 oMo(%)+5W(9
6D Fig. 1 shows the relationship between cr@-1-1oMo@)+5W(# and N1 content, with regard to stress corrosion cracking resistance under severe corrosive environments. That is, Or, Ni.

Or-N with various Mo and W contents
i-Mo system, Or-Ni-W system, and Or-Ni −
M.

- W series steel is melted, cast, and forged to form a slab with a thickness of 219-50 mm, then heated to 1200°C to start hot rolling. , the plate thickness is 1
When the temperature reached 0III, the temperature reached 1000°C, and hot rolling was carried out to the near thickness with a processing rate of 30% up to the finishing temperature of 900°C, followed by cooling at a processing rate of 22% for the purpose of improving strength. After additional processing, the resulting steel plate is rolled at right angles to the rolling direction to a thickness of 2. ．． X width = lOn x length =
A 75 mm test piece was cut out, and the second
Using the three-point support beam jig shown in the figure, the test piece was 0.
H2S and CO at 10 atm H2S and 10 atm CO under a tensile stress equivalent to 2% yield strength.
20 t NaO2 solution saturated with 2 (temperature: 150°C)
A stress corrosion cracking test was conducted by immersing the test piece in water for 1000 hours, and after the test, the presence or absence of cracking in the test piece was observed.

Based on these results, the inventors independently established the following conditional expression: Or%) +l OMo@+5W (%i) The relationship shown in the figure became clear. In FIG. 1, the O mark indicates no cracking, and the X mark indicates cracking.

From the results shown in Figure 1, Or(a)+10M0(4
)+5W(4) is less than 50% and the N1 content is less than 35 inches, it is clear that the desired excellent stress corrosion cracking resistance cannot be obtained.

In addition, in the pipe material of this invention, B is an unavoidable impurity.
, Sn, Pb, and Zn each in a range of 0.1% or less does not impair the characteristics of the pipe material of the present invention.

B. Hot working conditions The wall thickness reduction rate at 1000℃ or less during hot working is 1
The reason why it is set to 0% or more is because if the wall thickness reduction rate is less than 10 inches, the degree of processing is too low, and the fine crystal grains that are essential for imparting the desired high strength and excellent ductility to the pipe material are sufficiently formed. This is because it cannot be done. Also, the finishing temperature was set to 800.
The reason why the temperature is set to be higher than 800°C is that carbides that cause deterioration of corrosion resistance will precipitate if the finishing temperature is lower than 800°C.

In addition, during hot processing, the heating temperature should be set to 1050 to 1
It is desirable to set the temperature to 250°C, which means that the heating temperature is 10°C.
If it is below 50°C, the deformation resistance during hot working will not be too high and the working itself will be difficult, but undissolved intermetallic compounds and carbides will remain and cause deterioration of toughness and corrosion resistance. On the other hand, if the heating temperature exceeds 1250° C., the hot deformability will be significantly reduced, and hot working is not difficult.

C0 cold working conditions As mentioned above, in the method of the present invention, cold working is performed in a state where the crystal grains have been refined by hot working to improve strength. If the thickness is less than 10 mm, the desired high strength cannot be achieved, while if the wall thickness reduction rate exceeds 60%, the deterioration of ductility and toughness will be significant. The wall thickness reduction rate was set at 10 to 60%.

By applying the above component composition and processing conditions, it is possible to manufacture oil country tubular goods that have high strength with a 0.2% proof stress of 85 kgf/- or more, and have excellent stress corrosion cracking resistance as well as ductility and toughness. It is.

Next, the method for manufacturing oil country tubular goods of the present invention will be specifically explained using examples and comparing with comparative examples.

In each of the examples, a molten metal having the composition shown in Table 1 was heated in a conventional electric furnace, an Ar-oxygen decarburization furnace (AOD furnace) for the purpose of desulfurization and N addition, and further dephosphorization as necessary. After melting using an electroslag melting furnace (ESR furnace) for the purpose of melting, it was cast into an ingot with a diameter of 500 mm, and then hot forged at a temperature of 1200°C to form an ingot with a diameter of 150 mm. A billet is formed, and in this case, for the purpose of evaluating hot workability, it is observed whether or not cracks occur in the billet, and then the billet is heated under the hot working conditions shown in Table 1. The present invention was produced by forming a blank tube with an outer diameter of 6011φ x wall thickness of 4mm by extrusion processing, and then cold working at the wall thickness reduction rate shown in Table 1. Alloy tube material 1-27
, Comparative Alloy Tube Materials 1 to 9, and Conventional Alloy Tube Materials 1 to 4 were manufactured, respectively.

Comparative alloy tube materials 1 to 9 have a content of any one of the constituent components or one of the manufacturing conditions (shown with the manufacturing formula in Table 1) of the present invention. It was manufactured under conditions outside the range, and all conventional alloy tube materials had known compositions.
The pipe material 1 conforms to JIS-8US 316, and the same pipe material 2 conforms to JIS-8US 316.
IISUS3108, IISUS3 has a composition corresponding to Incoloy 800, and IISUS4 has a composition corresponding to rIslIsus 329Jl.

Next, the resulting alloy tube materials 1 to 27 of the present invention and comparative alloy tube materials 1 to 9. Then, a test piece with a length of 20 degrees was cut out from each of the conventional alloy tube materials 1 to 4, and a portion corresponding to 60° was cut off along the length direction of this test piece. As shown in the front view in the figure, a bolt is passed through and tightened with a nut to apply a tensile stress equivalent to 0.2% yield strength to the outer surface of the tube, and the H2S partial pressure is applied to the test piece S in this state. H2S - 10 atm Co2 - 20% at 0.1 atm, 1 atm, and 20 atm, respectively
A stress corrosion cracking test was conducted by immersing the sample in a NaC4 solution (liquid temperature: 150°C) for 1000 hours, and the presence or absence of stress corrosion cracking after the test was investigated. The results are shown in Table 2 together with the presence or absence of cracking during hot forging, the tensile test results, and the impact test results.

In Table 2, all marks ○ indicate those with no cracks, while marks X indicate those with cracks.

From the results shown in Table 2, comparative alloy tube materials 1 to 9 were inferior in at least one of the following properties: hot workability, stress corrosion cracking resistance, and strength.
All of the alloy tube materials 1 to 27 of the present invention have excellent hot workability and stress corrosion cracking resistance, and also have high strength and good hot workability, but have relatively low strength. It is clear that this material has even better properties than conventional alloy tube materials 1 to 4, which have low stress corrosion cracking resistance and are inferior in stress corrosion cracking resistance.

As mentioned above, oil country tubular goods manufactured by the method of the present invention have particularly high strength and excellent stress corrosion cracking resistance, and are therefore suitable for oil and natural gas extraction in harsh environments where these properties are required. Of course, it also exhibits extremely excellent performance when used as geothermal well pipes.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between N1 content and Or(%)-)10MO@-4-5W@ regarding the stress corrosion cracking resistance of alloys, and Figures 2 and 3 are for plate-like and It is a figure which shows the aspect of the stress corrosion cracking test on a tubular test piece. Applicant Sumitomo Metal Industries Co., Ltd. Agent Tomi 1) Kazuo Continued from page 1 0 Author Takeo Kudo Inside Sumitomo Metal Industries Central Technology Research Laboratory, 1-3 Nishinagasu Hondori, Amagasaki City 0 Author Akio Ikeda Inside the Sumitomo Metal Industries, Ltd. Central Technology Research Laboratory, 1-3 Nishinagasu Hondori, Amagasaki City.0 Inventor: Daiji Moroishi Inside the Sumitomo Metal Industries, Ltd. Central Technology Research Laboratory, 1-3 Nishinagasu Hondori, Amagasaki City.

Claims (1)

[Claims] (1) C: 0.05% or less, Si: 1.0%
Below, Mn: 2.0% or less, P: 0.030% or less,
S: 0.005 chi or less, sol, AQ: 0.5
% or less, Ni: 35-60%. Contains Cr: 22.5-35%, Mo: 4t
16% and W: less than 8%, has a composition (or more weight %) with the remainder consisting of Fe and unavoidable impurities, and Or (%) + 10 Mo (~ 9 + 5 W
(t4≧50%. 1.5chi≦Mo(%9+-wm<4%. A method for producing high-strength oil country tubular goods with excellent stress corrosion cracking resistance, characterized by hot working under conditions and then cold working at a wall thickness reduction rate of 10 to 60%. (2) O: 0.05% or less, Si: 1.0%
Below, Mn: 2.0% or less, P: 0.030% or less, S
: 0.005% or less + 5ob-All : 0.
5% or less, Ni: 35-60%. Or: 22.5 to 35%, Mo: less than 4% and W: less than 8%,
Furthermore, it contains one or two of Ou: 2% or less and Co: 2% or less, and has a composition (the above weight %) in which the remainder is Fe and unavoidable impurities, and Or (
%) + 1 o Mo (Si) + 5 W (91
)≧50chi. An alloy that satisfies the conditions of 1.5%≦MO (~9 +-W @ < 4%) is hot-processed under the conditions of a wall thickness reduction rate of 10% or more at 1000°C or less and a finishing temperature of 800°C or more. A method for producing high-strength oil country tubular goods with excellent stress corrosion cracking resistance, characterized by processing and subsequently cold working at a wall thickness reduction rate of 10 to 60%. (3) O: 0.05% Below, Si: 1.0%
Below, Mn: 2.0% or less, P: 0.030% or less, S
:0. O05 inches or less I EJOl, A1: 0.5 inches or less, Ni: 35 to 60 inches. (:r: Contains 22.5 to 35%, contains one or two of Mo: less than 4% and W: less than 8%, and further contains rare earth elements 20, 10% or less, Y20 .20%
One or two of the following: Mg: 0.10% or less, Ti: O-5% or less, and Ca: O, 1096 or less
Cr(51;)+l OMo(%)+5W%≧5
0%. 1.5q6≦MO(a)+-w (working 4chi) An alloy that satisfies the conditions is hot worked at a wall thickness reduction rate of 10chi or more at 1000°C or less and a finishing temperature of 800°C or more. A method for producing high-strength oil country tubular goods with excellent stress corrosion cracking resistance, which is characterized by performing cold working at a wall thickness reduction rate of 10 to 60 inches. (4) C: 0.05% or less , Sl: 1.0% or less,
Mn: 2.0 inches or less, P: 0.030 inches or less, S: 0.
Below 005chi, sot, fiJ! , : 0.5%
Hereinafter, Ni: 35 to 60%. Contains Or: 22.5 to 35%, contains one or two of Mo: less than 4% and W: less than 8%, and further contains Cu: 2% or less and Co: 2% or less. 1
One or two species and rare earth elements: 0.10% or less. Y: 0.20% or less, Mg: 0.10% or less,
Contains one or more of Ti: 0.5% or less and Ca: 0.10% or less, and the remainder is Fe.
and unavoidable impurities (weight%), and Or (!A+ 10 Mo (%) + 5 W
(%9≧50%. 1.5%≦MO(a) 10-W(4) 〈4h. : A method for manufacturing high-strength oil country tubular goods having excellent stress corrosion cracking resistance, which is characterized by hot working at a temperature of 800° C. or higher, and then cold working at a wall thickness reduction rate of 10 to 60 inches. (5) C: 0.05% or less, Si2 1.0% or less, Mn: 2.0% or less, P: 0.030% or less, S:
0. 005 inches or lessr 5oAAQ: 0.5 inches or less,
N: 0.05~063chi, Ni: 35~60%,
Or: Contains 22.5 to 35%, contains one or two of Mo: less than 4% and W: less than 8%, and the remainder is Fe and unavoidable impurities (wt%). Has and C! r (%il + 10 Mo (%
9 + 5 W%)≧50chi. 1.5%≦Mo(hook+-w(%)<4%) An alloy that satisfies the conditions of 1.5%≦Mo(hook+-w(%)<4%. A method for producing high-strength oil country tubular goods with excellent stress corrosion cracking resistance, characterized by cold working at a wall thickness reduction rate of 10 to 60 inches. (6) O: 0.05 % or less, Si: 1-04
Below, Mn-2.0% or less, P: 0.030% or less, S
:0. O05 or less, soL, A1: 0.5 or less, N: 0.05-0.3%, N1: 35-60%, Or
: Contains 22.5 to 35%, contains one or two of Mo: less than 4% and W: less than 8%, and further contains one of O: 2% or less and Co: 2% or less. It has a composition (by weight %) containing one or two species and the remainder is Fe and unavoidable impurities, and cr(hook+1 oMo(4+5w(9!il≧50%.1.5chi≦MO() 4) An alloy that satisfies the conditions of 10-W (a) <4 h. is hot-worked under the conditions of a wall thickness reduction rate of 10% or more at 1000°C or less and a finishing temperature of 800°C or more, and then A method for producing high-strength oil country tubular goods with excellent stress corrosion cracking resistance, characterized by cold working with a wall thickness reduction rate of 10 to 60%. (7) 0: 0.05% or less, Si: 1 .0% or less,
Mn: 2.0% or less, P: 0.030% or less, S: 0.
005 inches or less, sot, AA: 0.5 inches or less, N
:0.05~0.3%, Ni: 35~60%, Or
: 22.5 to 35%, Mo: less than 44 and w: less than s%, one or two of them, rare earth element = 0.10% or less, Y: 0.20
% or less, Mg: 0.10% or less, Ti: 0.
5% or less, and Oa: 1 of 0.10% or less
contains one or more species, has a composition (or more by weight) consisting of residual force EFe and unavoidable impurities, and cr(%9+l OMo(!@+5w(%f)≧
50 chi. 1.5chi≦Mo(4)+, w(4)<4chi. An alloy that satisfies the following conditions is hot worked at a wall thickness reduction rate of 10% or more at 1000'c or less and a finishing temperature of -800°C or more, and then subsequently processed at a wall thickness reduction rate of 10 to 60%. A method for manufacturing high-strength oil country tubular goods with excellent stress corrosion cracking resistance, which is characterized by cold working. (8) C: 0.05% or less, Si: 1. O
% or less + Mn: 2.0% or less, P: 0.030% or less, S: 0. O05chi or less r sot, M: 0.5
% or less, N: 0.05-0.3%, Ni: 3
Contains 5-60%, Or222.5-35%, Mo
: Less than 4% and w: One or two of less than 64
Contains seeds, further Cu: 2% or less and Cio: 2
% or less and rare earth element: 0.1
0% or less, Y2O,, 20% or less, Mg:O,1
0% or less, T1: 0.5% or less, and ca: 0.
10% or less of one or more of the following, and has a composition (weight %) in which the remainder is Fe and unavoidable impurities, and Or@+lOMo(19+5W@≧50%). 1. 5%≦Mo@)+-wn<4%. An alloy that satisfies the following conditions is hot-worked at a wall thickness reduction rate of 10 inches or more at 1000 tl or less and a finishing temperature of 280°C or more, and then cooled at a wall thickness reduction rate of 10 to 60%. A method for producing high-strength oil country tubular goods with excellent stress corrosion cracking resistance, which involves special processing.