EA013146B1 - Oil well pipes for expansion in well and two-phase stainless steel used for oil well pipes for expansion - Google Patents

Abstract

An oil well pipe for expansion, according to the invention, is expanded in a well. The oil well pipe for expansion, according to the invention, is made from two-phase stainless steel which has a chemical composition containing, in terms of mass %, from 0.005 to 0.03% carbon, from 0.1 to 1.0% silicon, from 0.2 to 2.0% manganese, up to 0.04% phosphorus, up to 0.015% sulfur, from 18.0 to 27.0% chromium, from 4.0 to 9.0% nickel, up to 0.040% aluminum, and from 0.05 to 0.40% nitrogen, with the remainder being iron and impurities, and has a structure having an austenite content of 40-90%. The oil well pipe for expansion, according to the invention, has a yield strength of 276-655 MPa and a uniform elongation more than 20%. Therefore the oil well pipe for expansion, according to the invention, has excellent expansibility.

Description

FIELD OF THE INVENTION

The present invention relates to an oil gauge and duplex stainless steel pipe, and in particular, an oil gauge pipe to be expanded in a well, and to duplex stainless steel used for these oil gauge pipe to be expanded.

State of the art

In general, when drilling a well (an oil well or gas well) from which oil or gas is produced, a plurality of oil gauge pipes called “casing pipes” are lowered into the wellbore drilled with a drill pipe to prevent the walls of the well from collapsing. The traditional method of constructing a well is as follows. First, the well is drilled to a predetermined depth and the first casing pipe is lowered. Then, when the well is additionally drilled to a predetermined depth, a second casing pipe having an outer diameter smaller than the inner diameter of the deflated first casing pipe is lowered. Thus, according to the traditional method of constructing the well, the outer diameters of the run-down casing are successively reduced as the well is drilled deeper. Therefore, as the oil well deepens, the inner diameters of the casing in the upper part of the well (near the surface of the earth) increase. As a result of this, the drilling area increases, which dramatically increases the cost of drilling.

A new method of reducing the drilling area and thus lowering the cost of drilling is disclosed in Japanese Patent 7-507610 A and the explanatory note to the international publication XVO 98/00626. The method proposed in these documents is as follows. A casing pipe C3 is lowered into the well, having an outer diameter less than the inner diameter ΙΌ1 of the casing pipes C1 and C2 already lowered into the well. Then, the deflated casing C3 is expanded so that its inner diameter becomes equal to the inner diameter ΙΌ1 of the previously deflated casing pipes C1 and C2, as shown in FIG. 1. According to the method, the casing is flared inside the well, and therefore there is no need to increase the drilling area if the oil well being constructed is deep. Therefore, the drilling area can be reduced. In addition, the number of required steel pipes can be reduced, since there is no need for large casing pipes.

Thus, pipes of an oil gauge for flaring in a well should have the ability to uniform deformation during flaring (hereinafter referred to as "the ability of the pipe to flare"). In order to obtain a high index of the ability of the pipe to be expanded, it is necessary to provide the ability to deform without local compression during processing, in other words, the uniform elongation, which can be estimated by the tensile test, must be high.

In particular, as shown in the drawing, in the region of the socket 10, where the casing is vertically overlapped, the degree of expansion of the pipe is maximum. Considering the degree of flaring in the area of the socket, it should be noted that the uniform elongation of the pipe of the oil product range for flaring is preferably more than 20%.

Japanese Patent 2005-146414 A proposes a seamless tube of oil grade for expansion. The structure of the proposed oil range pipe includes a ferrite transformation phase and low-temperature transformation phases (such as bainite, martensite and bainitic ferrite phase) and has a high ability of the pipe to be expanded. However, the uniform elongation of each test specimen in the proposed embodiment does not exceed 20% (see Japan Patent 2005-146414 A, i-E1 in Tables 2-1 and 2-2). Therefore, the above-disclosed region of the socket cannot be deformed uniformly.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an oil-grade tube for flaring with a high flaring ability. In particular, it relates to an oil gauge pipe having a uniform elongation of more than 20%.

To solve the problem, the inventors studied the homogeneous elongation of various types of steel. As a result, the inventors found that duplex stainless steel containing predetermined chemical components has a uniform elongation significantly exceeding that for carbon steel and martensitic stainless steel.

The inventors further studied and found that in order to obtain an oil grade pipe having a uniform elongation of more than 20%, the following requirements must be met.

(1) The proportion of austenite in duplex stainless steel is in the range of 40 to 90%. In this document, the proportion of austenite is measured by the following method. A test specimen is cut from an arbitrary part of the oil gauge pipe for expansion. The sample is mechanically ground and subjected to electrolytic etching in a KOH solution with a concentration of 30 mol%. The etched surface of the sample is examined under a 400-fold optical microscope using an eyepiece scale with a 25-linear grating and the proportion of austenite is measured using a needle probe according to A8TM E5 62.

(2) The yield strength is adjusted to a value in the range from 276 to 655 MPa. In this document

- 1 013146 the yield strength is a tensile stress of 0.2% according to A8TM. When the tube of the oil expansion gauge for expansion is left as hardened in a solid solution, the yield strength lies in the above range of values. Here, the expression "as hardened in a solid solution" means a state in which, after quenching of the solid solution, no other heat treatment or any other cold treatment was carried out, except for cold dressing.

The present invention is developed based on the above discovered facts, and the invention can be formulated as follows.

The oilfield tubulars for expansion according to the invention are expanded in a well. Pipes of an oil gauge for expansion according to the invention are formed from duplex stainless steel having a composition comprising, wt.%, From 0.005 to 0.03% C, from 0.1 to 1.0% 81, from 0.2 to 2.00 % Mn, at most 0.04% P, at most 0.015% 8, from 18.0 to 27.0% Cg, from 4.0 to 9.0% N1, at most 0.04% A1 and from 0, 05% to 0.40% Ν, and the rest is Te and impurities, and the structure includes a fraction of austenite in the range from 40 to 90%. Oil-grade pipes have a yield strength of 256 to 655 MPa and a uniform elongation of more than 20%.

As used herein, “uniform elongation” means deformation at the point of maximum load in a tensile test. The fraction of austenite is a fraction of the area of austenite.

Duplex stainless steel may additionally contain at most 2.0% Cu. Duplex stainless steel may further comprise one or more elements selected from the group comprising at most 4.0% Mo and at most 5.0% Duplex stainless steel may further comprise one or more elements selected from the group comprising at most 0, 8% T1, at most 1.5% V and at most 1.5% N6. Duplex stainless steel may further comprise one or more elements selected from the group consisting of at most 0.02% B, at most 0.02% Ca and at most 0.02% Md.

Duplex stainless steel according to the invention is used for the manufacture of the aforementioned oil gauges for expansion.

Brief Description of the Drawings

The drawing shows a schematic view to illustrate a new method of constructing a well from which oil or gas is extracted.

Preferred Embodiment

Embodiments of the invention will be described in detail below.

An oil gauge pipe according to an embodiment of the invention is formed of duplex stainless steel having the following chemical composition and metal structure. Hereinafter, “%” indicated for the elements indicate “wt.%”.

1. The chemical composition

C: from 0.005 to 0.03%.

Carbon stabilizes the austenite phase. In order for the effect to be effective, the C content is at least 0.005%. Although if the C content exceeds 0.03%, an easier deposition of carbide occurs, which reduces the corrosion resistance at the grain boundaries. Therefore, the content of C is from 0.005 to 0.03%.

8ί: 0.1 to 1.0%

Silicon deoxidizes steel. To ensure the effect, the content of 81 is not less than 0.1%. However, if the content of 81 exceeds 1.0%, intmetallic compounds are formed rapidly, which reduces the ability to be hot worked. Therefore, the content of 81 is from 0.1 to 1.0%.

MP: from 0.2 to 2.0%

Manganese deoxidizes and desulfurizes steel and, as a result of this, improves the ability to hot work. Manganese also increases the solubility of N in solid solution. To effectively ensure the effect, the content of Mn should be at least 0.2%. On the other hand, if the Mn content exceeds 2.0%, the corrosion resistance decreases. Therefore, the MP content is from 0.2 to 2.0%.

P: 0.04% or less

Phosphorus is an impurity that accelerates central segregation and reduces stress resistance to sulfide cracking. Therefore, the content of P is preferably as small as possible. Therefore, the content of P is not more than 0.04%.

8: 0.015% or less

Sulfur is an impurity and reduces the ability to hot work. Therefore, the content of 8 is preferably as small as possible. Therefore, the content of 8 is not more than 0.015%.

Sg: 18 to 27%

Chromium improves corrosion resistance to carbon dioxide. To ensure sufficient corrosion resistance under the action of carbon dioxide of duplex stainless steel, the Cr content should be at least 18%. On the other hand, if the Cr content exceeds 27%, the accelerated formation of intermetallic compounds occurs. Therefore, the content of Cr is from 18 to

- 2 013146

27.0%, preferably from 20.0 to 26.0%.

Νί: 4.0 to 9.0%

Nickel stabilizes the austenite phase. If the N1 content is too low, the amount of ferrite in the steel is excessive, and the characteristic property of duplex stainless steel is not manifested. The solubility of N in the solid solution of ferrite is small, and an increase in the amount of ferrite causes the precipitation of nitride, which affects the corrosion resistance. On the other hand, an excess of N1 reduces the amount of ferrite in the steel, and the characteristic property of duplex stainless steel is not manifested. In addition, an excess of N1 causes the deposition of the σ phase. Therefore, the N1 content is from 4.0 to 9.0%, preferably from 5.0 to 8.0%.

A1: 0.040% or less

Aluminum is an effective deoxidizer. However, if the A1 content exceeds 0.040%, the number of inclusions in the steel increases, which impairs the toughness and corrosion resistance. Therefore, the content of A1 is not more than 0.040%.

N from 0.05 to 0.40%

Nitrogen stabilizes the austenite phase and also improves the heat resistance and corrosion resistance of duplex stainless steel. In order to achieve an appropriate ratio between the ferrite phase and the austenite phase in steel, the N content should be at least 0.05%. On the other hand, if the content exceeds 0.40%, a defect arises attributed to the formation of voids. The toughness and corrosion resistance of the steel also deteriorate. Therefore, the N content is from 0.05 to 0.40%, preferably from 0.1 to 0.35%.

It should be noted that the rest of the duplex stainless steel according to the invention consists of It and impurities.

Duplex stainless steel for oilfield pipes for expansion according to an embodiment of the invention may additionally contain Cr instead of a portion of It, if necessary.

C: 2.0% or less

Copper is an optional element and improves the corrosion resistance of steel. However, an excess of Cu reduces the hot working ability of the steel. Therefore, the content of Cu is not more than 2.0%. It should be noted that to effectively ensure the above effect, the content of Cu is preferably not less than 0.2%. However, if the content of Cu is less than 0.2%, the above effect can be achieved only partially.

If necessary, duplex stainless steel for oilfield pipes for expansion according to an embodiment of the present invention may further comprise one or more elements selected from the group consisting of Mo and instead of part of It.

Mo: 4.0% or less: 5.0% or less

Molybdenum and tungsten are optional elements. These elements improve the resistance to the formation of shells during corrosion and the resistance to deposition of scale during corrosion. However, an excess content of Mo and an excess content causes easier deposition of the σ-phase, which embrittle the steel. Therefore, the Mo content is not more than 4.0%, and the content is not more than 5.0%. In order to effectively provide the above effect, the Mo content is preferably at least 2.0%, and the content is preferably at least 0.1%. However, if the Mo content and the content are less than the above limits, the above effect is only partially manifested.

If necessary, duplex stainless steel for oil gauges for expansion according to an embodiment of the invention may further comprise one or more elements selected from the group consisting of Τι, V and N0 instead of part of Her.

Τι: 0.8% or less

V: 1.5% or less

N0: 1.5% or less

Titanium, vanadium and niobium are optional elements. These elements improve the strength of steel. However, if the contents of these elements are redundant, the hot working ability of the steel is reduced. Therefore, the Τι content is 0.8% or less, the V content is 1.5% or less, and the N0 content is 1.5% or less. In order to effectively ensure the above effect, the content of Τι is preferably at least 0.1% and the content of V is preferably at least 0.05%. The content of N0 is preferably not less than 0.05%. However, if the contents of Τι, V, and N0 are less than the lower limits indicated above, the above effect can be achieved only partially.

Τί: 0.05% or less

Titanium (Τι) combines with N to form Τ ^ N and limits the coarsening of crystalline grains in the high temperature range. However, if the content of Τι exceeds 0.05%, Τι combines with C with about

- 3 013146 by the development of T1C, which reduces the toughness of steel. Therefore, the content of Τι is 0.05% or less. It should be noted that the effect of limiting the coarsening of crystalline grains is achieved to some extent if the content of Τι is approximately 0.001%, which is approximately the level of impurity content, while the effect is more clearly manifested if the content of Τι exceeds 0.005%.

Duplex stainless steel for an oil pipe assortment according to an embodiment of the invention further comprises one or more elements selected from the group consisting of B, Ca and MD instead of part of Her.

B: 0.02% or less

Ca: 0.02% or less

MD: 0.02% or less

Boron, calcium and manganese are optional elements. These elements improve the hot working ability of steel. However, if the contents of these elements are redundant, the corrosion resistance of the steel is reduced. Therefore, the content of B, the content of Ca and the content of MD in each case does not exceed 0.02%. In order to more efficiently provide the above effect, the content of B, the content of Ca and the content of MD in each case is preferably not less than 0.0002%. However, if the contents of B, Ca and MD are less than the lower limits, then the above effect can be achieved only partially.

2. Metal structure

Duplex stainless steel, which forms a steel pipe for the oil product range for expansion according to the invention, has a metal structure including a ferrite phase and an austenite phase. It is believed that the austenite phase, as a soft phase, determines the improvement in the uniform elongation index.

The proportion of austenite in steel ranges from 40 to 90%. In this document, the proportion of austenite is a fraction of the area, measured as follows. A test specimen is cut out from an arbitrary part of the oil gauge pipe for expansion and mechanically ground, and then the polished sample is subjected to electrolytic etching in a KOH solution with a concentration of 30 mol%. The etched surface of the sample is examined under a 400-fold optical microscope with eyepieces of a scale with a 25-linear grating and the proportion of austenite is measured by the needle probe method according to L8TM E562.

If the austenite fraction is less than 40%, the uniform elongation is reduced to 20% or less. On the other hand, if the proportion of austenite exceeds 90%, the corrosion resistance of the steel decreases. Therefore, the proportion of austenite is from 40 to 90%. The proportion of austenite is preferably from 40 to 70%, more preferably from 45 to 65%.

3. Method of production

The pipe for oil flaring according to the invention is made in the following way.

The molten steel having the above composition is cast and molded into billets. The resulting billet is subjected to hot processing and make of it an oil gauge pipe for expansion. As a hot working method, for example, the Mannesman method is used. As a hot treatment, hot extrusion or hot forging can be carried out. The manufactured flare pipe may be a seamless pipe or a welded pipe.

The tube for oil expansion for expansion after hot processing is subjected to hardening of a solid solution. The temperature of quenching of the solid solution at this time is from 1000 to 1200 ° C. If the quenching temperature of the solid solution is less than 1000 ° C, then the σ-phase is deposited, which embrittle the steel. The yield strength increases and exceeds 655 MPa due to deposition of the σ-phase, and therefore a uniform elongation reaches 20% or less. On the other hand, if the temperature of quenching of the solid solution exceeds 1200 ° C, then the fraction of austenite decreases significantly and becomes less than 40%. The solid solution quenching temperature is preferably from 1000 to 1175 ° C., more preferably from 1000 to 1150 ° C.

The flare pipe of the oil product according to the invention is in a “quenched solid solution” state (the so-called material in a quenched solid solution state). In particular, the pipe is used as a product immediately after hardening of the solid solution without performing other heat treatment and cold treatment (such as cold crimping or rolling on a pilgrim mill) except for cold dressing. Thus, since the pipe of the oil gauge for expansion according to the invention is in a “hardened solid solution” state, the yield strength can therefore lie in the range from 276 to 655 MPa (40 to 95 kg / sq. Inch). It is believed that in this case, uniform elongation exceeds 20%, and a high ability to expand is achieved even in the well. It should be noted that if the yield strength exceeds 655 MPa, the uniform elongation is 20% or less. An oil grade pipe for expansion requires strength of a certain level, and a yield strength of 276 MPa or more.

- 4 013146

It should be noted that if the cold treatment is carried out after quenching of the solid solution, the yield strength exceeds 655 MPa. Therefore, uniform elongation is less than 20%.

Example.

Many steel products having the chemical compositions shown in the table were cast and molded. The preforms obtained were hot forged and hot rolled, and a plurality of test steel plates were obtained having a thickness of 30 mm, a width of 120 mm, and a length of 300 mm.

Table

An experience Νο Chemical composition (in% by weight, the rest is Her and impurities) Sfuyaura Tzsimemeosh ^ "bebop VT ** with t (%) TV (MPa) Υ8 (MPa) willow (k) FROM & Mo R 8 SG No. A1 N Si Mo νν Τι V No. IN Sa Μι Steel according to the invention | one 0 016 0 39 0 49 0 023 00005 24 90 694 0020 02900 0DO 307 8 11 011 0 0025 ABOUT floor 1085 56 867 623 285 2 soy 0 25 039 0017 00007 22 00 540 0082 01400 0 10 290 ABOUT 8T 1070 68 735 490 480 IN 0022 040 090 0 016 00008 2519 "twenty 0030 01400 025 316 0 07 ABOUT at 1080 65 821 605 34 0 4 0020 0 65 0 016 00012 28 12 6 50 0020 01600 and 5T 1050 62 600 430 602 ? 0 014 9th 046 0 023 0 0003 24 88 659 0006 02716 0 46 Zoya 200 0.04 0 0023 0 0016 about 8T 1100 60 849 625 328 6 0 018 038 0 57 0 025 00000 26 37 ll 9 OD 02898 062 3 17 215 0 005 008 0 017 0 0028 00023 and 5T 1150 48 893 645 266 7 0020 048 1 51 0022 000) 1 22 39 5 74 0034 0) 650 320 0 ST 1050 85 734 484 484 8 0 018 0 45 1 56 0 021 00009 22 46 5 75 0026 01666 3.31 η 8T 1050 58 764 531 435 nine 0 017 0 31 0 87 0 017 00009 24 69 566 0 018 01200 026 307 0 002 η 8G 1060 68 760 1- "0- 403 10 0 024 "4" 0 98 0 027 00020 25 53 6 37 0 031 01700 048 3 1V ΰ 8T 1060 BEFORE 830 610 33 5 eleven 0018 0 45 085 0022 0 0007 00007 25 10 718 002V 0) 600 320 0 42 0 0021 R 6T 1060 55 805 605 520 876 96 about one one one 12 0 070 028 1 27 0009 020 002 0 020 00040 004 0007 004 from from 596 thirteen 0080 033 1 32 0014 0 0009 018 006 0030 00060 005 0009 006 from from 628 446 110 14 0007 0 23 1 20 0019 00005 015 0 031 00060 from "G 535 348 17 0 thirteen 0009 0 20 042 0 012 00014 11 90 5 33 0 020 00087 1.91 0 086 006 m from 914 761 200 sixteen 0 007 0 20 044 0017 00009 1203 544 0 025 0 0077 024 1.92 0071 006 m from 955 948 6 12 17 0007 020 042 0015 0 0006 1187 582 0 030 00076 1 91 0100 m from 890 843 915 eighteen 0007 020 044 0017 00009 12 05 5 43 0 022 0 0066 024 1 92 0069 006 m from 860 616 834 10 oooh 022 0 42 0016 0 0005 1189 6.42 0 021 00080 024 191 0097 008 m from 904 670 400 up 0009 0 ?.) 0 41 0013 0 0007 1194 6 41 0030 00090 023 1.91 0 096 006 m from 917 706 3 20 21 0021 0K5 106 0 016 0 0012 2612 6Y 0020 01700 ? .94 1 66 0 8T 880 60 970 701 160 22 0 020 0 59 1 10 0016 0 0012 26 01 660 0020 About 1600 2.87 1 95 R 8T 1350 32 930 643 "0 23 0 016 0 33 048 0 023 00005 24 60 686 0020 0 2900 060 304 205 0.09 & 0622 ϋ 8T + 1085 62 1110 1076 sixteen

Ό: duplex stainless steel; C: carbon steel; M: martensitic stainless steel; FROM: hardening and vacation; 8T: solid solution quenching, 8T + C ^: solid solution quenching + cold working, IE: uniform elongation.

In the table, the types of steel for the numbers of experiments are given in the column "structure". In the table, “Ό” stands for duplex stainless steel, “C” stands for carbon steel, and “M” stands for martensitic stainless steel. Regarding the table, experiments No. 1-11 and 21 and 23 relate to duplex stainless steel. Experiments No. 12-14 relate to carbon steel and experiments No. 15-20 relate to martensitic stainless steel.

Steel plates in experiments No. 1-23 were subjected to heat treatment, as described in the column "heat treatment" and cold treatment in the table. In particular, steel plates in experiments Nos. 1–11 were subjected to solid solution quenching in the temperature range from 1050 to 1150 ° С (“8Т” in the “heat treatment” column in the table). The solid solution quenching temperature for each of the steel plates is shown in the “Temperature 8T” column in the table. Steel plates in experiments No. 1-11 were each so-called “solid-hardened” material without any other heat treatment or cold working, such as cold crimping, after the solid solution was quenched.

Steel plates in experiments Nos. 12–20 were quenched at 920 ° С, and then tempered in the temperature range from 550 to 730 ° С (“рТ” in the “heat treatment” column in Table 1). The steel plate in experiment No. 21 was subjected to hardening of a solid solution at a temperature of less than 1000 ° C, and the steel plate in experiment No. 22 was subjected to hardening of a solid solution at a temperature of higher than 1200 ° C. Steel plates in experiments No. 21 and 22 are "hardened in solid solution" materials. The steel plate in experiment No. 23 was subjected to hardening of a solid solution at 1085 ° C followed by cold drawing.

Austenite fraction measurement

For steel plates made of duplex stainless steel in experiments No. 1-11 and 21 and 23 after heat treatment, the fraction of austenite was measured. In particular, a test piece was cut from each of these steel plates. The selected test samples were mechanically ground, and the ground test samples were subjected to electrolytic etching in a KOH solution with a concentration of 30 mol%. Etched surfaces of the samples were examined under an optical microscope of 400x magnification on the eyepiece scale with a 25-linear grating in 16 fields of view. A portion of austenite (%) was obtained for each of the observed fields of view. Austenite fractions (%) were measured using the needle probe method according to L8TM E562. The average value of the share of austenite (%) for each of their fields of view is given in the column "γ" in the table.

Tensile test

A round rod sample having an outer diameter of 6.35 mm and a parallel wall length of 25.4 mm was cut longitudinally from each steel plate 1-23 and subjected to a tensile test at room temperature. The values of yield strength (MPa) obtained during the tensile test are presented in the column "Υ8" in the table, the values of tensile strength (MPa)

- 5 013146 are given in the column "T8" in the table and the values of the uniform elongation (%) are given in the column "LE" in the table. The tensile stress of 0.2% according to the A8TM standard was determined as the yield strength (Υ8). The distortion of the sample at the point of maximum load was taken as uniform elongation (%).

Test results

Regarding table 1, the steel plates in experiments No. 1-11 each had a chemical composition, metal structure and yield strength in the ranges of values determined by the invention, and therefore, the values of their uniform elongation all exceeded 20%.

On the other hand, the steel plates in experiments No. 12-20 were not made of duplex stainless steel, and therefore the values of their uniform elongation did not exceed 20%.

The steel plate in experiment No. 21 was made of duplex stainless steel and had a chemical composition within the interval defined by the invention, but the temperature of the quenching of the solid solution was less than 1000 ° C. Therefore, the yield strength exceeded the upper limit of the interval defined by the invention, and the uniform elongation did not exceed 20%. This is probably due to the fact that the quenching temperature of the solid solution was low, and therefore no deposition of the σ phase occurred, which increases the yield strength.

Since the steel plate in experiment No. 22 exceeded 1200 ° C, the austenite fraction was less than 40%, and the uniform elongation did not exceed 20%. The steel plate in experiment No. 23 was not a “quenched in solid solution” material, but was cold worked after quenching of the solid solution. Therefore, the yield strength exceeded the upper limit of the interval defined by the invention, and the uniform elongation was not more than 20%.

Although embodiments of the present invention have been considered and illustrated in detail, it should be clearly understood that the explanations and example are given to show how the invention is carried out and should not be construed as limiting the nature and scope of the claims. The invention may be embodied in various modified forms without departing from the spirit and scope of the claims.

Industrial application

The oil expansion tubing and duplex stainless steel according to the invention are applicable to the oil grade tubing and are particularly applicable as the oil grade tubing for well expansion.

Claims (10)

CLAIM 1. The pipe of the oil gauges for flaring in the well, made of duplex stainless steel having a composition including, wt.%: C 0,005-0,03, δί 0,1-1,0, MP 0.2-2.0, P no more than 0.04, 8 no more than 0.015, Cr 18.0-27.0, N1 4.0-9.0, A1 no more than 0.04 and N 0.05-0.40, and the rest is Her and impurities, and the structure, including the share of austenite in the range from 40 to 90%, moreover, the specified oil grade pipe has a yield strength of 276 to 655 MPa and a uniform elongation of more than 20%. 2. The pipe of the oil gauge for expansion according to claim 1, wherein said duplex stainless steel further comprises not more than 2.0% Ca. 3. The pipe of the oil gauge for expansion according to claim 1 or 2, wherein said named duplex stainless steel additionally contains one or more elements selected from the group comprising not more than 4.0% Mo and not more than 5.0% ^. 4. A pipe of an oil gauge for expansion according to any one of claims 1 to 3, wherein said duplex stainless steel further comprises one or more elements selected from the group comprising not more than 0.8% T1, not more than 1.5% V and not more than 1.5% N6. 5. An oil range gauge pipe for expansion according to any one of claims 1 to 4, wherein said duplex stainless steel further comprises one or more elements selected from the group consisting of not more than 0.92% B, not more than 0.02% Ca and not more than 0.02% ppm. 6. Duplex stainless steel for the manufacture of an oil pipe gauge flared in a well, including, wt.%: C 0.005-0.03, 81 0.1-1.0, Mn 0.2-2.0, P no more than 0 04, 8 not more than 0.015, Cr 18.0-27.0, N1 4.0-9.0, A1 not more than 0.040 and N 0.05-0.40, and the rest is Her and impurities, moreover, said duplex stainless steel contains an austenite fraction of 40 to 90% and has a yield strength of 276 to 655 MPa and a uniform elongation of more than 20%. 7. Duplex stainless steel according to claim 6, additionally containing not more than 2.0% Ca. 8. Duplex stainless steel according to claim 6 or 7, additionally containing one or more elements from the group comprising not more than 4.0% Mo and not more than 5.0% 9. Duplex stainless steel according to any one of claims 6 to 8, further comprising one or more elements selected from the group consisting of not more than 0.8% T1, not more than 1.5% V and not more than 1.5% N6. 10. Duplex stainless steel according to any one of claims 6 to 9, further comprising one or more elements selected from the group consisting of not more than 0.02% B, not more than 0.02% Ca and not more than 0.02% Md.