JPS586927A - Production of high-strength oil well pipe of high stress corrosion cracking resistance - Google Patents

Abstract

PURPOSE:To produce titled oil well pipes by hot working and alloy contg. >=1 kind of Mo and W, as well as Ni and Cr and consisting of the balance Fe and holding this at specific temps. then cold woking the same. CONSTITUTION:The alloy which contains, by weight %, <=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, contains >=1 kind of <4% Mo and <8% W, and, if necessary, contains >=1 kind of <=2% Cu and <=2% Co, further contains <=0.10% rare earth elements, <=0.20% Y, <=0.10% Mg, >=1 kind of <=0.5% Ti and <=0.10% Ca or both and consisting of the balance substantially Fe and which satisfies the equationsI, II is subjected to the following treatments: It is hot-worked under the conditions wherein the thickness reduction rate at temps. lower than the recrystallization temp. is kept at >=10%, then it is heat-treated under the conditions of holding it for <=2hr at the temps. between the lower limit and upper limit temps. deg.C calculated by the equations III, IV, after which it is cooled worked at 10-60% thickness reduction ratios.

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 10,000 m 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 anti-corrosion measure for oil country tubular goods, it is known to introduce a corrosion suppressant called an inhibitor, but this method is often not effective for use in, for example, 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 hashing, Incoloy, and Hastelloy (all trade names) for the production of oil country tubular goods, but so far, there are no reports regarding these alloys. H2S
The details of the corrosion behavior of -CO2-C1'' in an oil well environment have not yet been fully elucidated, and at present it does not have the high strength required for oil country tubular goods for deep wells.

Therefore, from the above-mentioned viewpoint, the present inventors investigated deep wells and severe corrosive environments, especially I(2s -ca2- ct-
As a result of conducting research to manufacture oil country tubular goods with high strength and excellent stress corrosion cracking resistance that can sufficiently withstand oil drilling in the oil well environment of (a) H2S-C02-CL'' The main type of corrosion is stress corrosion cracking, but the behavior of stress corrosion cracking in this case is completely different from that of general austenitic stainless steel.In other words, general stress corrosion cracking is Cr7 On the other hand, in the oil well environment mentioned above, the influence of H2S is greater than that of Ct-.

(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-C1- environment depends on the contents of +cr, Ni, Mo, and W, and the corrosion resistance is maintained by the surface film made of these components. These components also increase the resistance to stress corrosion cracking, and in particular, Mo is more resistant than Cr.
Mo is 10 times more effective than W, and Mo is twice as effective as W.
+10Mo(%1l-175W(%)≧50%.

165%≦Mo(# + + W (%) <’%.

While satisfying the conditional expression, the Ni content should be 35 to 60%.
, If the Or content is 22.5 to 35 inches, H2S-Co2, which is extremely corrosive, can be used even in cold processed materials.
A surface film exhibiting excellent resistance to stress corrosion cracking in -Ct- oil well environments, particularly in adverse environments of 150° C. or lower, can be obtained.

(a) Ni 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 O, O'O
C) If it is reduced to 'i' or less, the hot workability of the tube material will be significantly improved.

(g) P content as an unavoidable impurity is 0.003
% or less, hydrogen cracking susceptibility significantly decreases.

(h) Cu: 2% or less and Co: as alloy components
Corrosion resistance can be further improved by containing one or two of the following.

(1) Rare earth elements: 0.10% or less as alloy components;
y: o, 20% or less, Mg: 0.10% or less, T1
:. , 5%yT, and ica: 0.10%U'T.

') 'C) (7) 1 ``'' When the j' type or two or more types are contained, the hot workability is further improved.

(J) In order to ensure the desired high strength, the alloy having the above composition should be heated at a temperature of preferably 1050 to 1250°C.
After heating to a temperature within the temperature range of The processing is to form fine recrystallized grains in the post-process heat treatment, thereby ensuring high strength and good ductility. (Foundation) and the same empirical formula: 16Mo (@
-) -10w(@+10Cr(@+777) Heat treatment is performed under the condition of holding for 2 hours or less at a temperature between the upper limit temperature (6) calculated by @+777 to form fine recrystallized grains as described above, In this case, if there is undissolved carbide that degrades corrosion resistance, it will be dissolved, and the pipe material after the above heat treatment is finally subjected to cold working at a wall thickness reduction rate of 10 to 60%. Therefore, it is necessary to strengthen the processing.

The findings shown in (a) to 0) above were obtained.

Therefore, this invention was made based on the above knowledge, and (:': 0.05% or less, S1: 10
% or less, Mn; 2.0% or less, p: 0.030
%below.

Preferably p:o for the purpose of further improving hydrogen cracking resistance.
, 003% or less, S: 0.005% or less, preferably S: O, OOO' for the purpose of further improving hot workability.
7 inches or less, sot, All! : 015% or less, N
i: 35-60%.

Contains 22.5 to 35% of Cr, and one or two of M(,: less than 4% and W: less than 8%,
Furthermore, if necessary, N: 0.05-0.3%, C
u: 2% or less, CQ: 2% or less, rare earth element: O,
10 or less, Y: 0.20 or less, Mg: 0.10
% or less, Ti = 0.5% or less, ゛ and Ca: 0.10
% or less, and the remainder is F.
It has a composition consisting of e and unavoidable impurities (the above weight %, below all indications of 饅 means weight %), and Cr
(%) + 10 Mo (%) + 5 W (%)
≧50%.

1.5%≦MoC%)++W℃)〈4%.

An alloy that satisfies the conditions is hot worked under conditions where the wall thickness reduction rate below the recrystallization temperature is 10% or more, and then 26
ol, gc (lower limit temperature (g) calculated by @-1-1300 and l 6Mo (%) + 10 W (%) +
l 0Cr(%9 +77'7 upper limit temperature calculated
After heat treatment at a temperature between 6) for 2 hours or less, cold working at a wall thickness reduction rate of 10 to 60 inches produces high-strength oil country tubular goods with excellent stress corrosion cracking resistance. This method is unique in its method.

Next, in the method for manufacturing oil country tubular goods of the present invention, the reason why the component composition, heat treatment conditions, and wall thickness reduction rate in hot working and cold working are limited to the above excessive values will be explained below.

A. Ingredient composition (a) C The lower the C content, the more suppressed the precipitation of carbides, so the heating temperature and heat treatment temperature during hot working can be lowered. This effectively acts to increase strength. Therefore, it is desirable that the C content is as low as possible, but if the C content is 0.0
If it exceeds 5%, intergranular stress corrosion cracking tends to occur, so the upper limit was set at 0.05%.

(b) SI Sl is a necessary component as a deoxidizing component, but if its content exceeds 1.0%, hot workability will deteriorate, so the 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.

(a) p The P component as an unavoidable impurity has a content of 0.0
If it exceeds 30%, the effect of increasing the stress corrosion cracking susceptibility appears, so it is necessary to set the upper limit to Q, 030% to keep the stress corrosion cracking susceptibility to a low state. It has also been found that as the P content is reduced, the hydrogen cracking resistance rapidly improves after reaching 0.003 cm. When hydrogen crackability is required, the P content is desirably 0.0030% or less.

(e) S The S component as an unavoidable impurity has a content of o,...
If it exceeds 5%, 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 if its content is lowered to 0.000 'i'%
On the contrary, if the S content is reduced to 0.000'7% or less, the hot workability will be further improved. is desirable.

(f) AI! .

AQ is effective as a deoxidizing component like Sl and Mn, and sot, At! Since it does not impair the properties of the pipe material even if the content is up to 0.5%, the content was determined to be 0.5% or less in terms of sol and fiJl content.

(g) Ni The N1 component has the effect of improving the stress corrosion cracking resistance of the pipe material, but if its content is less than 35 nickels, the desired excellent stress corrosion cracking resistance cannot be secured. 60
Even if the content exceeds 35%, no further improvement effect on stress corrosion cracking resistance appears, and the content was set at 35% to 60%, taking economic efficiency into account.

(It is a component that significantly improves stress corrosion cracking resistance in coexistence with CR acid components, Ni, Mo, and W components.
Even if the content is less than 22.5%, hot workability will not be improved; on the contrary, in order to secure the desired stress corrosion cracking resistance, the content of Mo and W must be increased to that extent. Since this would be economically disadvantageous, 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 35%.

(i) Mo and W As mentioned above, these components have an equal effect of improving stress corrosion cracking resistance when coexisting with Ni and Cr, but Mo: 4% or more and W: 8% or more, respectively. H2S-CO whose environmental temperature is 150℃ or less even if it is contained more than %
In the corrosive environment of 2-C1-, no further improvement effect appeared, and considering economic efficiency, the respective contents were changed to MO
: Less than 4% 2w: Less than 8%. In addition, regarding the content of Mo and W, the conditional expression: Mo (%il + +
The reason for specifying W (%') is that the atomic weight of W is about twice that of MO, and the effect is about 10, which is equivalent.
If this value is less than 1.5%, the desired stress rotten wood cracking resistance cannot be obtained, especially under the above-mentioned adverse environment of 150°C or less.On the other hand, even if this value is 4- or more, the above-mentioned excessive It is not economical to contain the necessary amounts of Mo and W, so the value of Mo (4 + 4 W (9)) is set to 1.5 to 4%.
It is set as less than

(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. If the content exceeds 0.3%, melting and ingot making will become difficult, so the content should be set at 0.05 to 0.3% (Cu and c).

These components have a uniform effect of improving the corrosion resistance of the pipe material, and co has a solid solution strengthening effect, so
Cu is added as necessary when even better corrosion resistance is required, but if it exceeds 2%, hot workability deteriorates, while CO should not be added if it exceeds 2%. Since no further improvement effect was observed, the upper limits were set as Cu: 2% and Co: 2%, respectively.

(4 Rare earth elements + Y r Mg + Tl + and Ca These components have a uniform effect to further improve hot workability, so when hot working is carried out under severe conditions, they can be added as necessary. Rare earth elements: 0.10% and Y: 0.20%, respectively.

Mg: 0.10%, Ti: 0.5%, and Ca:
Even if the content exceeds 0.10%, no improvement effect on hot workability is observed, and in fact, deterioration phenomena even appear.
°□゛°・ Therefore, the respective contents are: 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% or less.

(m) Cr (%) -1-10Mo (@+ 5
W (%) Figure 1 shows stress corrosion cracking resistance under severe corrosive environments.
This shows the relationship between W (%l) and N1 content. That is, Cr, Ni, Mo.

and Cr-Ni-Mo systems with various W contents.

Cr-Ni-W system, and Cr-Ni-Mo-W
After melting, casting, and forging a slab with a thickness of 50 mm, this is heated to 1200°C to start hot rolling. From the time when the temperature reached 10 mm, that is, from the time when the temperature reached 1000 ° C. at which recrystallization does not proceed, the processing rate was set to 30%, and the plate thickness was hot rolled to the order of 7.
Next, this plate material was held at a temperature of 1000°C for 30 minutes and then subjected to water cooling heat treatment, followed by a processing rate of:
22% cold working is applied, and the resulting steel plate has a thickness of 2mm x width = 10mm x length near 5mm in the rolling direction and angle.
Cut out a test piece, and use the three-point support beam jig shown in FIG.
H2S and CO2 at 10 atm H2S and 10 atm C02 with the addition of tensile stress corresponding to % proof stress.
A stress corrosion cracking test was carried out by immersing the specimen in a 20% NaC4 solution (temperature = 150°C) saturated with 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 set the conditional expression:
Cr (%) + 1 o+v○ (@+5W←) and N1
It has become clear that there is a relationship between the content and the stress corrosion cracking resistance shown in FIG. In FIG. 1, the O mark indicates no cracking, and the X mark indicates cracking. From the results shown in Figure 1, it is clear that the desired excellent stress corrosion cracking resistance cannot be obtained when the value of Cr(@+10 Mo (chi) It is clear that there is no.

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

B. Hot working conditions The wall thickness reduction rate below the recrystallization temperature during hot working is 10
% or more is because if the wall thickness reduction rate is less than 10%, sufficient fine recrystallized grains, which are essential for imparting the desired high strength and excellent ductility to the pipe material, will be formed in the post-process heat treatment. This is because it is not possible. In addition, during hot processing,
It is desirable to set the heating temperature to 1050 to 1250°C. This is because if the heating temperature is less than 1050°C, the deformation resistance during hot processing will be too high and the processing itself will be difficult, and the Intermetallic compounds and carbides in the melt remain and cause deterioration of toughness and corrosion resistance.On the other hand, heating temperatures exceeding 1250°C result in a significant decrease in hot deformability, making hot working difficult. This is for the reason.

C0 heat treatment conditions As mentioned above, this heat treatment is performed to sufficiently form fine recrystallized grains1, but the formation of fine recrystallized grains in this case is 260 pupil C (%) - 4 - 1300 16Mo (%) + l OW (%
) + l 0cr (@ -4-777 This is done by maintaining the temperature between the upper limit temperature (G) calculated in 2 hours or less. Calculation formula for this lower limit temperature: z
Calculation formula for 6oiogc (%) + 1300 and upper limit temperature: 16 Mo (@ +10W (%) + l 0C
r ((A) +777 is determined empirically based on the results of numerous tests, and below the above lower limit temperature it is not possible to sufficiently measure the formation of the specified fine recrystallization.
On the other hand, the heat treatment temperature exceeded the above upper limit temperature9
If the holding time exceeds 2 hours, the crystal grains will become coarse and the effect brought about by hot annealing will disappear, making it impossible to secure the desired high strength and toughness, so heat treatment conditions was limited to the above-mentioned excess.

In this case, if undissolved intermetallic compounds and carbides remain, they will cause deterioration of corrosion resistance, but by setting the heat treatment temperature to the above-mentioned lower limit temperature or higher, they can be completely dissolved.

, D. Cold working conditions In addition, in this invention, as described above, cold working is performed after heat treatment to improve the strength, but if the cold working reduces the wall thickness by less than 10 inches, the desired strength cannot be secured. On the other hand, if cold working is performed at a wall thickness reduction rate of more than 60%, the deterioration of ductility and toughness becomes significant. It was established.

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

Next, the method for producing oil country tubular goods according to 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 rrartφ, and then this ingot was hot forged at a temperature of 1200°C to form an ingot with a diameter of 150 gφ. 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. A blank tube with an outer diameter of 60 mm and a wall thickness of 4 mm is formed by extrusion processing, and then heat treatment conditions shown in Table 1 (cooling after treatment is water cooling in both cases) and By applying heat treatment and cold working at a wall thickness reduction rate, the alloy tube materials 1 to 27 of the present invention. 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 (indicated with an asterisk in Table 1) of the present invention. All conventional alloy tube materials have known compositions, and are manufactured under conditions that are outside the range.
The pipe material 1 is JIS SUS 316, and the pipe material 2 is JIS SUS 316.
-8US31O8, same 3,・ is Incoloy 800,
No. 4 has a composition corresponding to J'lS-8US 329J1.

Next, the resulting alloy tube materials 1 to 27 of the present invention and comparative alloy tube materials 1 to 9. A test piece with a length of 20 + 111 + L was cut out from the conventional alloy tube material 1-4, and a portion corresponding to 60° was cut off along the length direction of the test piece. Penetrate the bolt as shown in the figure, tighten it with a nut, and attach it to the outer surface of the tube.
A tensile stress equivalent to 2% proof stress was applied to the test piece S in this state, and H2S partial pressures were set to 0.1 atm, 1 atm, and 20 atm, respectively. H2S -10 atm CO2-
A stress corrosion cracking test was conducted by immersing the sample in a 20% NaCt 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, the ○ mark indicates that no cracking occurred, while the x mark indicates that cracking occurred.

From the results shown in Table 2, comparative alloy tube materials 1 to 9 were inferior in at least one of 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 the drawing]

Figure 1 is a diagram showing the relationship between Ni content and Cr (%9 + 5 W (%)) regarding the stress corrosion cracking resistance of alloys, and Figures 2 and 3 are for plate-like and It is a diagram showing the mode of the stress corrosion cracking test on the tube i, 1-state test piece. Inside the Sumitomo Metal Industries, Ltd. Central Research Laboratory, 1-3 Nishi-Nagasu Hondori, Amagasaki City 0 Inventor Moroishi Inuji Inside the Sumitomo Metal Industries, Ltd. Central Technology Research Laboratory, 1-3 Nishi-Nagasu Hondori, Amagasaki City

Claims (1)

[Claims] (1) C: 0.05% or less T S 1: l, O
% or less, Mn: 2.0 inches or less, P: 0.030 inches or less, S: 0.005% or less, so L, M: 0.
5% or less, Ni: 3 ff) M-60%, Cr: 2
Contains 2.5-35%, Mo: less than 4% and W: 8
%, the remainder has a composition consisting of Fe and unavoidable impurities (weight %), and cr(@+ 1 oMo(% 9+ 5 W(#≧50
%. An alloy satisfying the condition of 1.5CH≦MO(%)++W(@<4%. 260
The lower limit temperature (g) calculated by pupil C(4)+1300,
16 M. ((6)+10W(→+10Cr(→+Maximum temperature calculated in 11 A method for producing high-strength oil country tubular goods having excellent stress corrosion cracking resistance. (2) C: 0.05% or less, Sl: 1.0% or less, Mn: 2.0% or less, P : 0.030 inch or less, S
: 0.005% or less, soL, Al: 0.5% or less, Ni: 35-60%, Cr: 22.5-35
%, contains one or two of MO: less than 4% and W: less than 8%, and further contains one or two of Cu: 2% or less and Co: 2% or less. However, the residue has a composition (more than % by weight) consisting of Fe and unavoidable impurities, and Cr C + 10 Mo (@ + 5 W
(%)≧50%. 1.5chi ≦ MO (%) + + W (%) < 4%
. An alloy that satisfies the following conditions is hot worked under conditions where the wall thickness reduction rate below the recrystallization temperature is 10% or more, and then 2601
The lower limit temperature calculated by 0gC(9))+1300)・
and l 6Mo(@+l OW(%)-)-10Cr(
After heat treatment under the condition of holding for 2 hours or less at a temperature between
A method for producing high-strength oil country tubular goods with excellent stress corrosion cracking resistance, which is characterized by cold working with a wall thickness reduction rate of 0%. (3) C: 0.05% or less, Si: 1.0% or less, Mn: 2.0 or less, P: 0.030 or less, S
:0. O05 or less r sot, Al: 0.5%
Below, Ni: 35-60%, Cr: 22.5-3
5%, Mo: less than 4%, and Im or two of WaS%, and further rare earth elements: 0
．． 10 or less, '1': 0.20% or less, Mg:
0.10% or less, Ti: 0.5- or less, and Ca
Cr ('J + 10 Mo ('l) +5 W (%
)250%. 1.5%≦MO (%) + + W (%) < 4%
. An alloy that satisfies the conditions is hot worked under conditions where the wall thickness reduction rate below the recrystallization temperature is 10- or more, and then 260
Lower limit temperature (g) calculated by 1ogC(5)+1300
and 16Mo (%) + l OW (%) + 10Cr (
@+'7 After heat treatment at a temperature between the upper limit temperature (6) calculated in '77 for 2 hours or less, 10 to 6
A method for producing high-strength oil country tubular goods having excellent stress corrosion cracking resistance, which is characterized by cold working at a wall thickness reduction rate of 0. (4) C: 0.05% or less, Si: 1.0
% or less, Mn: 2.0% or less, P: 0.030
% or less, S: 0.005% or less, somAQ: 0
．． 5% or less, Ni: 35-60%, Cr: 22.5
~35%, contains one or two of Mo: less than 4% and W: less than 8%, and further contains one or two of Cu: 2% or less and Co: 2% or less. and rare earth elements: 0.10% or less. Y: 0.20% or less, Mg: 0.10% or less, T
i: 0.5% or less, and Ca: 0.10% or less, and has a composition (wt %) in which the remainder is Fe and unavoidable impurities, And, C
r (%) + 10M0 (%) + 5W (%) 250%. An alloy that satisfies the condition of 1.5%≦Mo(4++w (%)<4%.
Lower limit temperature calculated by 01ogC(a)+1300
1・1(Rito, 16Mo(%)−1−10W(%)+
Upper limit temperature (6
) is heat-treated at a temperature of 2 hours or less, and then cold-worked at a wall thickness reduction rate of 10 to 60%. Manufacturing method. (5) C: 0. Oa% or less, Si: 1.0% or less, Mn: 2.0% or less, p: o, oso% or less, S
: 0.005 q6 or less, som7u: 0.5% or less, N: 0.05 to 0.3%. Contains Ni: 35-60%, Cr: 22.5-35%, Mo2 less than 4% and W2 less than 1.
CrC%)+
10M0 (@+5 W (%) 250%. 1.5%≦MO (%) + + W (%) < 4%
. An alloy that satisfies the conditions is hot worked under conditions where the wall thickness reduction rate below the recrystallization temperature is 10% or more, and then
Lower limit temperature (G) calculated from Pupil C1%)-4-1300
and 16M0 (%) -1-10W (%) -1-10
Upper limit temperature (6) calculated from Cr (%) -1-77'7
After heat treatment at a temperature between 2 hours or less,
A method for producing high-strength oil country tubular goods having excellent stress corrosion cracking resistance, characterized by cold working at a wall thickness reduction rate of 10 to 60 inches. (6) c: 0.05% or less, Si: 1.0% or less, Mn: 2.0% or less, p: 0.030% or less, S: 0.005% or less, soL, I%l: o, 5
Below 1, N: 0.05 to 0.3. Ni: 35-60%, 'Cr: 22.5-35
%, contains one or two of Mo: less than 4% and w: less than 6, and further contains one or two of Cu: 2% or less and C0: 2% or less. , a composition in which the remainder consists of Fe and unavoidable impurities (more than % by weight)
), and cr(% + 10 Mo(%) + 5 W(%)
≧50chi. 1.5%≦Mo(%)Jushi W Yu)〈4%. An alloy that satisfies the conditions is hot worked under conditions where the wall thickness reduction rate below the recrystallization temperature is 10% or more, and then
1. The lower limit temperature calculated by gC(@-)-1300 (Rito, 16Mo(@+10 W(%)-1-10Cr(%
)-1-'i''i''i' After heat treatment at a temperature between the upper limit temperature (C) calculated by 'i''i''i' for 2 hours or less, 1
A method for producing high-strength oil country tubular goods having excellent stress corrosion cracking resistance, characterized by cold working at a wall thickness reduction rate of 0 to 60%. (l'f) C: 0.05% or less, 3i: 1.0% or less, Mn: 2.0% or less, P: 0.030% or less, s
:o, oo5chi or less, sot, Ai! : 015
% or less, N: 0.05-0.3%. Contains Ni: 35-60%, Cr: 22.5-35%, MO: less than 4% and W: less than 8%.
Contains one or two species, and further contains rare earth elements: 0.10%
Contains one or more of the following: Y: 0.20% or less, Mg: 0.10% or less, Ti: 0.5% or less, and Ca: 0.10% or less, and has no residue. has a composition (more than % by weight) consisting of Fe and unavoidable impurities, and
Or(%i) +10 Mo(%l -1-5W (%
)≧50chi. An alloy that satisfies the condition of 1.5%≦Mo (plow + W (a) × 4 cm) is hot worked under the condition that the wall thickness reduction rate below the recrystallization temperature is 10 cm or more, and then 26 cm
The lower limit temperature (6) calculated from ol, gc 1%) -1-130,0 and 16Mo (%) -1-10W (%)
+10 Cr (%) -1-7'/'i' After heat treatment at a temperature between the upper limit temperature (6) calculated by 'i' for 2 hours or less, a wall thickness reduction rate of 10 to 60%7 A method for producing 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.
0% or less, Mn 2.0% or less, P: 0.030% or less, S: 0.005% or less, sot, M:'0.
5% or less, N: 0.05-0.3%. Contains Ni: 35-60%, Cr: 22.5-35%, MO: less than 4% and w: less than 86 ID, and further contains Cu: 2% or less and CO: One or two of 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
Containing one or more of 101% or less,
Composition where the remainder is Fe and unavoidable impurities (weight%)
and Cr(@+10Mo(@+5W(%)25
0%. An alloy satisfying the condition of 1.5%≦MoC%)++W (% to 4%) is hot worked under conditions where the wall thickness reduction rate below the recrystallization temperature is 10% or more, and then 260%
1ogCI%)-1-1300 lower limit temperature (
g) and l 6Mo (%) -) - 10W (%) + l 0
Cr (%) After heat treatment at a temperature between the upper limit temperature (6) calculated by +777 for 2 hours or less, 10
A method for producing high-strength oil country tubular goods having excellent stress corrosion cracking resistance, characterized by cold working at a wall thickness reduction rate of ~60%.