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    • 专利摘要:
    a high-strength seamless stainless steel tube for tubular petroleum products that excels in low temperature toughness, corrosion resistance by carbon dioxide, corrosion resistance and crack stress by sulfide and resistance to crack stress by sulfide is described . the high-strength seamless stainless steel tube that has a yield strength of 862 mpa or more contains, in% by weight, c: 0.05% or less, si: 0.5% or less, mn: 0 , 15 to 1.0%, p: 0.030% or less, s: 0.005% or less, cr: 14.5 to 17.5%, ni: 3.0 to 6.0%, mo: 2.7 to 5.0%, cu: 0.3 to 4.0%, w: 0.1 to 2.5%, v: 0.02 to 0.20%, al: 0.10% or less, n: 0 , 15% or less, b: 0.0005 to 0.0100%, and the balance is fe and unavoidable impurities, and where the c, si, mn, cr, ni, mo, cu, en satisfy a specific formula, and cu, mo, w, cr, and ni satisfy a specific formula. the stainless steel tube has more than 45% martensite phase, 10 to 45% ferrite phase and 30% or less retained austenite phase. ferrite grains have a maximum crystal grain size of 500 µm or less as measured in an inspection of a continuous region of 100 mm2 assuming that grains having a crystal orientation difference of no more than 15 ° represent the same grains in electron backscatter diffraction (ebsd).
    公开号:BR112019017105A2
    申请号:R112019017105
    申请日:2018-01-23
    公开日:2020-04-14
    发明作者:Eguchi Kenichiro；Yuga Masao；Ishiguro Yasuhide；Kamo Yuichi
    申请人:Jfe Steel Corp；
    IPC主号:
    专利说明:

    Descriptive Report of the Invention Patent for STAINLESS STEEL TUBE WITHOUT HIGH RESISTANCE SEWING FOR PETROLEUM TUBULAR PRODUCTS AND THE SAME PRODUCTION METHOD.
    TECHNICAL FIELD [001] The present invention relates to a high strength seamless stainless steel tube preferred for use in oil well and gas well applications such as crude oil wells and natural gas wells (hereinafter in this document, simply called tubular petroleum products). In particular, the invention relates to a high-strength seamless stainless steel tube preferred for use in tubular petroleum products and having excellent resistance to corrosion by carbon dioxide in a severe corrosive high temperature environment containing carbon dioxide gas (CO2) ) and chlorine ions (Cl), and excellent resistance to corrosion and cracking under sulfide stress (SCC resistance) under high temperature, and excellent resistance to cracking under sulfide stress (SSC resistance) under ambient temperature in an environment containing hydrogen sulfide (H2S). As used herein, high strength means strength with a yield strength in the order of 125 ksi, specifically a yield strength of 862 MPa or more.
    BACKGROUND OF THE TECHNIQUE [002] The rise in the price of crude oils, and the growing scarcity of oil resources has led to the active development of deep oil fields that were unthinkable in the past, and oil fields and gas fields in a harsh corrosive environment, or an acidic environment as it is also called, in which hydrogen sulfide and other corrosive gases are present. Such oil fields and gas fields are typically very deep, and involve
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    2/40 a severe high temperature corrosive environment in an atmosphere containing CO2, Cl · and H2S. Steel tube materials for tubular petroleum products intended for use in such an environment require high strength, and excellent corrosion resistance (resistance to corrosion by carbon dioxide, resistance to corrosion and cracking by sulfide and resistance to cracking by tension by sulfide).
    [003] Tubular petroleum products used for mining oil fields and gas fields in an environment containing carbon dioxide (CO2) chlorine (Cl ·) ions, and the like often use martensitic stainless steel tubes with 13% Cr. 13Cr modified martensitic stainless steels with a reduced carbon content and increased levels of other components such as Ni and Mo have also been widely used in recent years.
    [004] For example, PTL 1 describes a modified martensitic stainless steel (tube) that improves the corrosion resistance of a 13Cr martensitic stainless steel (tube). The stainless steel (tube) described in PTL 1 is a martensitic stainless steel that has excellent resistance to corrosion and excellent resistance to corrosion and cracking under tension by sulfide, and contains, in weight%, C: 0.005 to 0.05% , Si: 0.05 to 0.5%, Mn: 0.1 to 1.0%, P: 0.025% or less, S: 0.015% or less, Cr: 10 to 15%, Ni: 4.0 to 9.0%, Cu: 0.5 to 3%, Mo: 1.0 to 3%, Al: 0.005 to 0.2%, N: 0.005 to 0.1%, and the balance is Fe and unavoidable impurities, where the equivalent of Ni (Ni eq.) satisfies 40C + 34N + Ni + 0.3Cu 1.1 Cr - 1.8Mo = -10. Martensitic stainless steel has a tempered martensite phase, a martensite phase and a retained austenite phase, where the total fraction of the tempered martensite phase and the martensite phase is 60% or more and 90% or less, and 0 remaining is the retained austenite phase. This improves corrosion resistance and resistance to corrosion and cracking under sulfide stress in an environment.
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    3/40 containing wet carbon dioxide gas, and in an environment containing wet hydrogen sulfide.
    [005] Tubular petroleum products were developed for use in a corrosive environment of even higher temperatures (as high as 200 ° C). However, with the technique described in PTL 1, the desired corrosion resistance cannot be sufficiently guaranteed in a stable manner in such a high temperature corrosive environment.
    [006] This has generated a demand for a steel tube for tubular petroleum products that have excellent corrosion resistance and excellent resistance to corrosion and cracking under sulfide stress even when used in a high temperature corrosive environment. For this purpose, a wide variety of martensitic stainless steel tubes is proposed.
    [007] For example, PTL 2 describes a high-strength stainless steel tube that has excellent corrosion resistance of a composition containing, in% by weight, C: 0.005 to 0.05%, Si: 0.05 to 0 , 5%, Mn: 0.2 to 1.8%, P: 0.03% or less, S: 0.005% or less, Cr: 15.5 to 18%, Ni: 1.5 to 5%, Mo : 1 to 3.5%, V: 0.02 to 0.2%, N: 0.01 to 0.15%, and O: 0.006% or less, where Cr, Ni, Mo, W, and C satisfy a specific relational expression, and Cr, Mo, Si, C, Mn, Ni, Cu, and N satisfy a specific relational expression. The stainless steel tube has a structure that has a martensite phase as a basic phase and contains 10 to 60% ferrite phase and can additionally contain 30% or less of austenite phase, by volume. In this way, the stainless steel tube can have sufficient corrosion resistance even in a severe corrosive environment containing CO2- and Cl 'at a temperature as high as 230 ° C, and a high strength and high toughness stainless steel tube for products oil pipelines can be produced in a stable manner.
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    4/40 [008] PTL 3 describes a high strength stainless steel tube for tubular petroleum products that have high toughness and excellent resistance to corrosion. The technique described in PTL 3 produces a steel tube of a composition containing,%, by mass, C: 0.04% or less, Si: 0.50% or less, Mn: 0.20 to 1.80%, P: 0.03% or less, S: 0.005% or less, Cr: 15.5 to 17.5%, Ni: 2.5 to 5.5%, V: 0.20% or less, Mo: 1 , 5 to 3.5%, W: 0.50 to 3.0%, Al: 0.05% or less, N: 0.15% or less, and O: 0.006% or less, where Cr, Mo , W, and C satisfy a specific relational expression, and Cr, Mo, W, Si, C, Mn, Cu, Ni, and N satisfy a specific relational expression, and Mo and W satisfy a specific relational expression. The high strength stainless steel tube has a structure that has a martensite phase as a basic phase and contains 10 to 50% ferrite phase by volume. The technique allows the production of a high-strength stainless steel tube for tubular petroleum products having sufficient corrosion resistance even in a severe corrosive environment at high temperature containing CO2-, Cl- and H2S.
    [009] PTL 4 describes a high strength stainless steel tube that has excellent resistance to cracking under sulfide stress and excellent resistance to corrosion by carbon dioxide gas at high temperature. The technique described in PTL 4 produces a steel tube of a composition containing,%, by mass, C: 0.05% or less, Si: 1.0% or less, S: less than 0.002%, Cr: more than 16% and 18% or less, Mo: more than 2% and 3% or less, Cu: 1 to 3.5%, Ni: 3% or more and less than 5%, Al: 0.001 to 0.1%, and O: 0.01% or less, where 0 Mn and N satisfy a specific ratio in a phase of 1% or less of Mn, and 0.05% or less of N. The high strength stainless steel tube has a structure that is mainly a martensite phase, and that contains 10 to 40% of ferrite phase, and 10% or less of γ retained phase by volume. The technique allows the production of a steel tube
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    5/40 high strength stainless steel with excellent corrosion resistance. Corrosion resistance is sufficient even in a carbon dioxide gas environment as high as 200 ° C, and the stainless steel tube has sufficient crack resistance under sulfide stress even at low ambient gas temperatures.
    [0010] PTL 5 describes a stainless steel for tubular petroleum products that has a test voltage of 758 MPa or more. Stainless steel has a composition containing, in mass%, C: 0.05% or less, Si: 0.5% or less, Mn: 0.01 to 0.5%, P: 0.04% or less, S: 0.01% or less, Cr: more than 16.0 to 18.0%, Ni: more than 4.0 to 5.6%, Mo: 1.6 to 4.0%, Cu: 1.5 to 3.0%, Al: 0.001 to 0.10%, and N: 0.050% or less, where Cr, Cu, Ni, and Mo satisfy a specific relationship, and (C + N), Mn, Ni, Cu, and (Cr + Mo) satisfy a specific relationship. Stainless steel has a structure with a martensite phase, and 10 to 40% by volume of ferrite phase, in which the proportion of the ferrite phase that crosses a plurality of imaginary segments of 50 pm in length from the surface in the direction thickness and arranged in lines over a 200 pm region at a 10 pm step is greater than 85%. In this way, stainless steel for tubular petroleum products has excellent resistance to corrosion in a high temperature environment and excellent resistance to SCC at room temperature.
    [0011] PTL 6 describes containing, in% by mass, C: 0.05% or less, Si: 0.5% or less, Mn: 0.15 to 1.0%, P: 0.030% or less, S: 0.005% or less, Cr: 15.5 to 17.5%, Ni: 3.0 to 6.0%, Mo: 1.5 to 5.0%, Cu: 4.0% or less, W : 0.1 to 2.5%, and N: 0.15% or less, to satisfy -5.9 x (7.82 + 27C - 0.91 Si + 0.21 Mn - 0.9Cr + Ni - 1.1 Mo + 0.2Cu + 11N) - 13.0, Cu + Mo + 0.5W ~ 5.8, and Cu + Mo + W + Cr + 2Ni = 34.5. Thus, the high strength seamless stainless steel tube can have excellent corrosion resistance, including excellent
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    6/40 resistance to corrosion by carbon dioxide in a high temperature environment containing CO2- and Cl · as high as 200 ° C, and excellent resistance to cracking under stress by sulfide and excellent resistance to corrosion and stress cracking by sulfide in a corrosive environment containing H2S.
    REFERENCE LIST
    PATENT LITERATURE [0012] PTL 1: JP-A-H10-1755 [0013] PTL 2: JP-A-2005-336595 [0014] PTL 3: JP-A-2008-81793 [0015] PTL 4: WO2010 / 050519 [0016] PTL 5: WO2010 / 134498 [0017] PTL 6: JP-A-2015-110822
    SUMMARY OF THE INVENTION
    TECHNICAL PROBLEM [0018] Since the development of oil fields and gas fields in a severe corrosive environment continues, it is necessary that steel tubes for tubular petroleum products have high strength, excellent low temperature toughness and excellent corrosion resistance, including resistance to corrosion by carbon dioxide and resistance to corrosion and cracking under stress by sulfide (resistance to SCC) and resistance to cracking under stress by sulfide (resistance to SSC), even in a severe corrosive environment of high temperature containing CO2, Cl · - and H2S.
    [0019] However, it cannot be said that the techniques described in PTL 2 to PTL 5 are satisfactory in terms of providing excellent low temperature toughness and sufficient SSC resistance in an environment with a high partial pressure of H2S. This is due to the fact that crystal grains in a heated steel pipe material before drilling to improve hot workability increase
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    7/40 in size when the heating temperature is too high, and cannot provide a high tenacity value at low temperature. With a low toughness at a low temperature, the stainless steel tube cannot be used in cold climates. When the heating temperature is too low, the lack of ductility causes the inner and outer surfaces of the steel pipe to crack during the manufacture of the pipe. In tubular petroleum products that use such a steel pipe, sufficient SSC resistance cannot be achieved in the event that corrosive ions accumulate in the steel crack, or concentrate as corrosion progresses. A high tenacity value at low temperature cannot be achieved with the technique described in PTL 6.
    [0020] The present invention is intended to provide solutions to the previously mentioned problems of the related technique, and an objective of the present invention is to provide a seamless high strength stainless steel tube for tubular petroleum products having high strength and excellent toughness to low temperature and excellent corrosion resistance including excellent resistance to carbon dioxide corrosion, and excellent resistance to corrosion and cracking under sulfide stress and excellent resistance to cracking under sulfide stress, even in a severe corrosive environment as described above. The invention is also intended to provide a method for producing such a high strength seamless stainless steel tube.
    [0021] As used in this document, high strength means a flow resistance of 125 ksi (862 MPa) or more.
    [0022] As used in this document, excellent tenacity at low temperature means having an absorption energy of 100 J or more at -40 ° C as measured in a Charpy impact test performed with a notched test piece V (10 mm thick) according to J IS Z 2242.
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    8/40 [0023] As used in this document, excellent resistance to corrosion by carbon dioxide means that a test piece immersed in a test solution (20% aqueous solution by weight of NaCI; liquid temperature: 200 ° C; atmosphere of COzde gas 30 atm) loaded in an autoclave has a corrosion rate of 0.125 mm / y or less after 336 hours in the solution.
    [0024] As used in this document, excellent resistance to corrosion under stress by sulfide means that a test piece immersed in a test solution (a 20% aqueous solution by weight of NaCI; liquid temperature: 100 ° C an atmosphere of COzde gas 30 atm, and H2S atmosphere of 0.1 atm) that has an adjusted pH of 3.3 with the addition of an aqueous solution of acetic acid and sodium acetate in an autoclave does not crack even after 720 hours under an applied voltage equal to 100% of the yield limit.
    [0025] As used in this document, excellent resistance to cracking under tension by sulfide means that a test piece immersed in a test solution (a 20% aqueous solution by weight of NaCI; liquid temperature: 25 ° C an atmosphere of 0.9 atm CÜ2 gas, and 0.1 atm H2S atmosphere) that has an adjusted pH of 3.5 with the addition of an aqueous solution of acetic acid and sodium acetate in an autoclave does not crack even after 720 hours under an applied voltage equal to 90% of the yield limit.
    SOLUTION TO THE PROBLEM [0026] To achieve the above objectives, the present inventors carried out intensive studies of stainless steel tubes of a composition containing Cr from the perspective of corrosion resistance, with regard to several factors that can affect the low temperature toughness at -40 ° C. Studies have shown that a steel tube
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    9/40 high strength seamless stainless steel that has excellent resistance to corrosion by carbon dioxide and excellent resistance to corrosion and cracking under tension by sulfide at high temperature, in a corrosive high temperature environment containing CO2-, Cl · and H2S of 200 ° C, and in a corrosive environment of an atmosphere containing CO2, Cl · and H2S under a voltage applied close to the flow resistance can be obtained when the stainless steel tube has a composite structure that contains more than 45% martensite as a primary phase, 10 to 45% ferrite phase and 30% or less of austenite phase retained as a secondary phase, by volume.
    [0027] Another finding is that hot workability improves with a composition containing more than a certain amount of boron, and that, with such a composition, the grain growth during heating can be reduced without causing defects due to reduced ductility, even when a steel pipe material is heated to a temperature of 1200 ° C or less for the production of a seamless steel pipe, as will be described later. With the fine structure, low temperature toughness improves.
    [0028] After further studies, the present inventors found that the adjustment of the contents of C, Si, Mn, Cr, Ni, Mo, Cu, and N to satisfy the following formula (1) is important to provide the desired composite structure in a composition containing 14.5% by weight or more of Cr.
    Formula (1)
    -5.9 x (7.82 + 27C - 0.91 Si + 0.21 Mn - 0.9Cr + Ni - 1.1 Mo + 0.2Cu + 11N)> 13.0, [0029] where C , Si, Mn, Cr, Ni, Mo, Cu, and N represent the content of each element (% by mass).
    [0030] The left side of the formula (1) represents a value experimentally determined by the present inventors as an indi
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    10/40 ce which includes the probability of the ferrite phase occurring. The present inventors have found that adjusting the amount and type of alloying elements to satisfy formula (1) is important to obtain the desired composite structure.
    [0031] It has also been found that excessive generation of retained austenite can be reduced, and the desired high strength and resistance to cracking under sulfide stress can be provided by adjusting the Cu, Mo, W, Cr and Ni levels for satisfy the following formula (2).
    Formula (2)
    Cu + Mo + W + Cr + 2Ni <34.5, [0032] where Cu, Mo, W, Cr, and Ni represent the content of each element (% by mass).
    [0033] Another finding is that excellent low temperature toughness with an absorbing energy of Charpy at -40 ° C of 100 J or more can be obtained when a steel pipe material before drilling is heated to a temperature of 1200 ° C or less during the production of a seamless steel tube.
    [0034] Regarding the reasons why a composition that has a high Cr content of 14.5%, by weight, or more, a composite structure containing mainly a martensite phase, a ferrite phase and a retained austenite phase as a secondary phase, and containing Cr, Mo, and W each in an amount not less than a specific amount may have not only excellent resistance to corrosion by carbon dioxide but also excellent resistance to corrosion and cracking under stress by sulfide and excellent resistance to cracking under sulfide stress, the present inventors consider the following.
    [0035] The ferrite phase provides excellent resistance to honeycomb corrosion, and precipitates in a laminar manner in the lamination direction,
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    11/40 ie the axial direction of the tube. As the laminar structure is parallel to the direction of stress applied in a sulfide stress crack test and a sulfide stress corrosion and crack test, the cracks propagate in a way that divides the laminar structure into two parts. Consequently, crack propagation is suppressed, and SSC resistance and SCC resistance improve.
    [0036] Excellent resistance to corrosion by carbon dioxide occurs when the composition contains a reduced carbon content of 0.05%, by weight, or less, and 14.5%, by weight, or more than Cr, 3, 0%, by weight, or more of Ni and 2.7%, by weight, or more of Mo.
    [0037] The present invention is based on these findings, and was completed after further studies. Specifically, the foundation of the present invention is as follows.
    [0038] [1] A high strength seamless stainless steel tube for petroleum tubular products, the high strength seamless stainless steel tube having a flow resistance of 862 MPa or more with a composition that comprises, in % by weight, C: 0.05% or less, Si: 0.5% or less, Mn: 0.15 to 1.0%, P: 0.030% or less, S: 0.005% or less, Cr: 14.5 to 17.5%, Ni: 3.0 to 6.0%, Mo: 2.7 to 5.0%, Cu: 0.3 to 4.0%, W: 0.1 to 2, 5%, V: 0.02 to 0.20%, Al: 0.10% or less, N: 0.15% or less, B: 0.0005 to 0.0100%, and the balance is Fe and impurities unavoidable, and where C, Si, Mn, Cr, Ni, Mo, Cu, and N satisfy formula (1) below, and Cu, Mo, W, Cr, and Ni satisfy formula (2) below, [0039] in which the stainless steel tube has a structure that contains more than 45% of the martensite phase as a primary phase, 10 to 45% of the ferrite phase and 30% or less retained austenite phase as a secondary phase, by volume, and [0040] where the ferrite grains have a grain size of maximum stale of 500 pm or less as measured in an inspection of
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    12/40 a continuous region of 100 mm 2 assuming that the grains having a difference in crystal orientation of no more than 15 ° represent the same grains in electron backscattering diffraction (EBSD).
    Formula (1)
    -5.9 x (7.82 + 27C - 0.91 Si + 0.21 Mn - 0.9Cr + Ni - 1.1 Mo + 0.2Cu + 11N)> 13.0, [0041] where C , Si, Mn, Cr, Ni, Mo, Cu and N represent the content of each element (% by mass).
    Formula (2)
    Cu + Mo + W + Cr + 2Ni <34.5, [0042] where Cu, Mo, W, Cr and Ni represent the content of each element (% by mass).
    [0043] [2] The high-strength seamless stainless steel tube for tubular petroleum products according to item [1], in which the composition additionally comprises, in% by weight, at least one selected from Nb : 0.02 to 0.50%, Ti: 0.02 to 0.16% and Zr: 0.02 to 0.50%.
    [0044] [3] The high strength seamless stainless steel tube for tubular petroleum products according to item [1] or [2], in which the composition additionally comprises, in% by weight, at least one selected from REM: 0.001 to 0.05%, Ca: 0.001 to 0.005%, Sn: 0.05 to 0.20%, and Mg: 0.0002 to 0.01%.
    [0045] [4] The high-strength seamless stainless steel tube for tubular petroleum products according to any of items [1] to [3], in which the composition additionally comprises, in% by weight, at least one selected from Ta: 0.01 to 0.1%, Co: 0.01 to 1.0%, and Sb: 0.01 to 1.0%.
    [0046] [5] A production method of the high strength seamless stainless steel tube for tubular petroleum products of any of the items [1] to [4],
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    13/40 [0047] the method comprising:
    [0048] heating a steel pipe material to a heating temperature of 1200 ° C or less;
    [0049] working the hot steel pipe material to produce a seamless steel pipe of a predetermined shape; and [0050] to cool down and quench the seamless steel pipe worked in succession.
    ADVANTAGE EFFECTS OF THE INVENTION [0051] The present invention can provide a seamless stainless steel tube of high strength with high strength and excellent toughness at low temperature and also with excellent resistance to corrosion by carbon dioxide, excellent resistance to corrosion and cracking under sulfide stress and excellent resistance to cracking under sulfide stress, even in a severe corrosive environment as described above.
    MODALITY DESCRIPTION [0052] A high strength seamless stainless steel tube for tubular petroleum products of the present invention is a high strength seamless stainless steel tube that has a yield strength of 862 MPa or more, and an energy of absorption at -40 ° C of 100 J or more as measured by a Charpy impact test, and has a composition comprising, in mass%, C: 0.05% or less, Si: 0.5% or less, Mn: 0.15 to 1.0%, P: 0.030% or less, S: 0.005% or less, Cr: 14.5 to 17.5%, Ni: 3.0 to 6.0%, Mo : 2.7 to 5.0%, Cu: 0.3 to 4.0%, W: 0.1 to 2.5%, V: 0.02 to 0.20%, Al: 0.10% or less, N: 0.15% or less, B: 0.0005 to 0.0100%, and the balance is Fe and unavoidable impurities, where C, Si, Mn, Cr, Ni, Mo, Cu, and N satisfy formula (1) below, and Cu, Mo, W, Cr, and Ni satisfy formula (2) below.
    Formula (1)
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    14/40
    -5.9 x (7.82 + 27C - 0.91 Si + 0.21 Μη - 0.9Cr + Ni - 1.1 Mo + 0.2Cu + 11N)> 13.0, [0053] where C , Si, Mn, Cr, Ni, Mo, Cu, and N represent the content of each element (% by mass).
    Formula (2)
    Cu + Mo + W + Cr + 2Ni <34.5, [0054] where Cu, Mo, W, Cr, and Ni represent the content of each element (mass%).
    [0055] Seamless steel pipe is produced by heating a steel pipe material to a heating temperature of 1200 ° C or less, and the ferrite grains have a maximum grain size of 500 pm or less as measured in an inspection of a 100-mm 2 continuous region assuming that the grains having a crystal orientation difference of no more than 15 ° represent the same grains in electron backscattering diffraction (EBSD). [0056] The reasons for specifying the composition of the steel tube of the present invention are as follows. In the following description,% means mass percentage, unless otherwise specified.
    [0057] C: 0.05% or less [0058] Carbon is an important element in increasing the strength of martensitic stainless steel. In the present invention, the carbon is contained in an amount, preferably, 0.005% or more to provide the desired strength. A C content of more than 0.05% deteriorates the resistance to corrosion by carbon dioxide, and the resistance to corrosion and cracking under stress by sulfide. For this reason, the C content is 0.05% or less. Preferably, the lower limit of C content is 0.005%, and the upper limit of C content is 0.04%. More preferably, the lower limit of C content is 0.005%, and the upper limit of C content is 0.02%.
    [0059] Si: 0.5% or less
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    15/40 [0060] Silicon is an element that acts as a deoxidizing agent. This effect is achieved with a Si content of 0.1% or more. A Si content in excess of 0.5% deteriorates hot workability. For this reason, the Si content is 0.5% or less. Preferably, the lower Si content limit is 0.2%, and the upper Si content limit is 0.3%. [0061] Mn: 0.15 to 1.0% [0062] Manganese is an element that increases the strength of steel. In the present invention, manganese must be contained in an amount of 0.15% or more to provide the desired strength. A Mn content in excess of 1.0% deteriorates toughness. For this reason, the Mn content is 0.15 to 1.0%. Preferably, the lower limit of Mn content is 0.20%, and the upper limit of Mn content is 0.5%. Most preferably, the lower limit of Mn content is 0.20%, and the upper limit of Mn content is 0.4%.
    [0063] P: 0.030% or less [0064] In the present invention, phosphorus should preferably be contained in the least amount possible, as this element deteriorates corrosion resistance, including resistance to corrosion by carbon dioxide, resistance to honeycomb corrosion and crack resistance under sulfide stress. However, a P content of 0.030% or less is acceptable. For this reason, the P content is preferably 0.030% or less, preferably 0.020% or less, more preferably 0.015% or less.
    [0065] S: 0.005% or less [0066] Preferably, the sulfur should be contained in the least amount possible, as this element is highly detrimental to hot workability, and interferes with a stable operation of the tube manufacturing process. However, normal tube production is possible when the S content is 0.005% or less. For this reason, the S content is 0.005% or less. The S content is preferably 0.002%
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    16/40 or less, more preferably, 0.0015% or less.
    [0067] Cr: 14.5 to 17.5% [0068] Chromium is an element that forms a protective coating and contributes to improving corrosion resistance. In the present invention, chromium must be contained in an amount of 14.5% or more to provide the desired corrosion resistance. With a Cr content of more than 17.5%, the ferrite fraction becomes excessively high, and it is not possible to provide the desired high strength. This also causes precipitation of intermetallic compounds during tempering and deteriorates toughness at low temperature. For this reason, the Cr content is 14.5 to 17.5%. Preferably, the lower Cr content limit is 15.0%, and the upper Cr content limit is 17.0%. More preferably, the lower Cr content limit is 15.0%, and the upper Cr content limit is 16.5%.
    [0069] Ni: 3.0 to 6.0% [0070] Nickel is an element that adds resistance to the protective coating and improves corrosion resistance. Nickel also increases the strength of the steel through hardening by solid solution. Such effects are achieved with a Ni content of 3.0% or more. With a Ni content of over 6.0%, the stability of the martensite phase decreases and the resistance decreases. For this reason, the Ni content is 3.0 to 6.0%. Preferably, the lower limit of Ni content is 3.5%, and the upper limit of Ni content is 5.5%. More preferably, the lower Ni content limit is 4.0%, and the upper Ni content limit is 5.5%. [0071] Mo: 2.7 to 5.0% [0072] Molybdenum is an element that improves the resistance to honeycomb corrosion due to Cl · and low pH, and improves the crack resistance under sulfide stress and the resistance to corrosion and cracking under sulfide stress. In the present invention, molybdenum must be contained in an amount of 2.7% or more. With a content of
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    17/40
    Less than 2.7%, sufficient corrosion resistance cannot be achieved in a severe corrosive environment. Molybdenum is an expensive element and a high Mo content in excess of 5.0% causes precipitation of intermetallic compounds, and deteriorates toughness and resistance to honeycomb corrosion. For this reason, the Mo content is 2.7 to 5.0%. Preferably, the lower Mo content limit is 3.0%, and the upper Mo content limit is 5.0%. More preferably, the lower Mo content limit is 3.3%, and the upper Mo content limit is 4.7%.
    [0073] Cu: 0.3 to 4.0% [0074] Copper is an important element that adds resistance to the protective coating, and suppresses the entry of hydrogen into the steel. Copper also improves resistance to cracking under sulfide stress, and resistance to corrosion and cracking under sulfide stress. Copper must be contained in an amount of 0.3% or more to obtain such effects. A Cu content of more than 4.0% leads to CuS precipitation in the grain boundaries, and deteriorates hot workability and corrosion resistance. For this reason, the Cu content is 0.3 to 4.0%. Preferably, the lower limit of Cu content is 1.5%, and the upper limit of Cu content is 3.5%. More preferably, the lower Cu content limit is 2.0%, and the upper Cu content limit is 3.0%.
    [0075] W: 0.1 to 2.5% [0076] Tungsten is a very important element that contributes to improving the strength of steel. This element also improves resistance to corrosion and cracking under sulfide stress, and resistance to cracking under sulfide stress. When contained with molybdenum, tungsten improves the crack resistance under sulfide stress. Tungsten must be contained in an amount of 0.1% or more to obtain such effects. A high W content of over 2.5% causes precipitation of intermetallic compounds and deteriorates toughness. For this reason, the W content is 0.1
    Petition 870190079651, of 16/08/2019, p. 28/58
    18/40 to 2.5%. Preferably, the lower limit of W content is 0.8%, and the upper limit of W content is 1.2%. More preferably, the lower limit of W content is 1.0%, and the upper limit of W content is 1.2%.
    [0077] V: 0.02 to 0.20% [0078] Vanadium is an element that improves the strength of steel through precipitation hardening. Such an effect can be obtained when the vanadium is contained in an amount of 0.02% or more. A V content of more than 0.20% deteriorates toughness. For this reason, the V content is 0.02 to 0.20%. Preferably, the lower limit of V content is 0.04%, and the upper limit of V content is 0.08%. More preferably, the lower limit of V content is 0.05%, and the upper limit of V content is 0.07%.
    [0079] Al: 0.10% or less [0080] Aluminum is an element that acts as a deoxidizing agent. Such an effect can be obtained when aluminum is contained in an amount of 0.001% or more. With an Al content of more than 0.10%, the amount of oxide becomes excessive, and the toughness deteriorates. For this reason, the Al content is 0.10% or less. Preferably, the lower limit of Al content is 0.01%, and the upper limit of Al content is 0.06%. More preferably, the lower Al content limit is 0.02%, and the upper Al content limit is 0.05%.
    [0081] N: 0.15% or less [0082] Nitrogen is an element that significantly improves resistance to honeycomb corrosion. Such an effect becomes more pronounced when nitrogen is contained in an amount of 0.01% or more. A nitrogen content of more than 0.15% results in the formation of several nitrides and the toughness deteriorates. For this reason, the N content is 0.15% or less. The N content is preferably 0.07% or less, more preferably 0.05% or less.
    [0083] B: 0.0005 to 0.0100%
    Petition 870190079651, of 16/08/2019, p. 29/58
    19/40 [0084] Boron contributes to increased strength, and improved hot workability. Boron is contained in an amount of 0.0005% or more to achieve these effects. A boron content of more than 0.0100% produces only an additional marginal hot workability-enhancing effect, if any, and reduces toughness at low temperature. For this reason, the B content is 0.0005 to 0.0100%. Preferably, the lower limit of B content is 0.0010%, and the upper limit of B content is 0.008%. More preferably, the lower B content limit is 0.0015%, and the upper B content limit is 0.007%.
    [0085] In the present invention, specific components are contained in specific amounts, and C, Si, Mn, Cr, Ni, Mo, Cu, and N satisfy the following formula (1), and Cu, Mo, W, Cr, and Ni satisfy the following formula (2).
    Formula (1)
    -5.9 x (7.82 + 27C - 0.91 Si + 0.21 Mn - 0.9Cr + Ni - 1.1 Mo + 0.2Cu + 11N)> 13.0 [0086] In the formula (1 ), C, Si, Mn, Cr, Ni, Mo, Cu, and N represent the content of each element (% by mass).
    [0087] The left side of formula (1) represents a value determined as an index that includes the probability of the ferrite phase occurring. By containing the alloying elements of formula (1) in quantities adjusted to satisfy formula (1), a composite structure of the martensite phase and the ferrite phase with an additional retained austenite phase can be obtained in a stable manner. Therefore, the amount of each alloying element is adjusted to satisfy formula (1) in the present invention. It should be noted that when the alloying elements shown in formula (1) are not contained, the contents of these elements on the left side of formula (1) are considered to be 0 percent.
    Petition 870190079651, of 16/08/2019, p. 30/58
    20/40
    Formula (2)
    Cu + Mo + W + Cr + 2Ni <34.5 [0088] In the formula (2), Cu, Mo, W, Cr and Ni represent the content of each element (% by mass).
    [0089] The left side of formula (2) represents a value recently derived by the present inventors as an index that includes the probability of occurrence of retained austenite. When the value on the left side of formula (2) exceeds 34.5, an amount of the retained austenite becomes excessive, and the desired high strength cannot be provided. The resistance to cracking under sulfide stress, and resistance to corrosion and cracking under sulfide stress also deteriorate. For this reason, Cu, Mo, W, Cr, and Ni are adjusted to satisfy formula (2) in the present invention. The value on the left side of formula (2) is preferably 32.5 or less, more preferably 31 or less.
    [0090] In addition to the basic components mentioned above, the composition contains the balance of Fe and unavoidable impurities. O (oxygen) is acceptable as unavoidable impurities: 0.01% or less.
    [0091] The following optional elements may be contained in the present invention, as needed. At least one selected from Nb: 0.02 to 0.50%, Ti: 0.02 to 0.16%, and Zr: 0.02 to 0.50%, and / or at least selected from REM: 0.001 to 0.05%, Ca: 0.001 to 0.005%, Sn: 0.05 to 0.20%, and Mg: 0.0002 to 0.01%, and / or at least selected from Ta: 0.01 to 0.1%, Co: 0.01 to 1.0%, and Sb: 0.01 to 1.0%.
    [0092] At least one selected from Nb: 0.02 to 0.50%, Ti: 0.02 to 0.16%, and Zr: 0.02 to 0.50% [0093] Nb, Ti and Zr are elements that contribute to increase resistance, and can be contained by selection, as needed.
    Petition 870190079651, of 16/08/2019, p. 31/58
    21/40 [0094] In addition to increasing strength, niobium contributes to improving toughness. Niobium is contained in an amount, preferably, 0.02% or more to provide these effects. An Nb content of more than 0.50% deteriorates toughness. For this reason, niobium, when contained, is contained in an amount of 0.02 to 0.50%.
    [0095] In addition to increasing the strength, titanium contributes to improving the crack resistance under tension by sulfide. Titanium is contained in an amount, preferably 0.02% or more, to achieve these effects. When the titanium content is more than 0.16%, coarse precipitates occur, and the toughness and resistance to corrosion and cracking under sulfide stress deteriorate. For this reason, titanium, when contained, is contained in an amount of 0.02 to 0.16%.
    [0096] In addition to increasing strength, zirconium contributes to improving resistance to corrosion and cracking under tension by sulfide. Zirconium is contained in an amount, preferably, 0.02% or more to achieve these effects. A Zr content of more than 0.50% deteriorates toughness. For this reason, zirconium, when contained, is contained in an amount of 0.02 to 0.50%.
    [0097] At least one Selected from REM: 0.001 to 0.05%, Ca: 0.001 to 0.005%, Sn: 0.05 to 0.20%, and Mg: 0.0002 to 0.01% [0098 ] REM, Ca, Sn and Mg are elements that contribute to improve the resistance to corrosion and cracking under sulfide stress and can be contained by selection, as needed. Preferred levels to provide such an effect are 0.001% or more for REM, 0.001% or more for Ca, 0.05% or more for Sn, and 0.0002% or more for Mg. It is not economically advantageous to contain REM in excess of 0.05%, Ca in excess of 0.005%, Sn in excess of 0.20%, and Mg in excess of 0.01%, as the effect is not proportional
    Petition 870190079651, of 16/08/2019, p. 32/58
    22/40 to the content, and it becomes saturated. For this reason, REM, Ca, Sn and Mg, when contained, are contained in amounts of 0.001 to 0.05%, 0.001 to 0.005%, 0.05 to 0.20%, and 0.0002 to 0.01% , respectively.
    [0099] At least one Selected from Ta: 0.01 to 0.1%, Co: 0.01 to 1.0%, and Sb: 0.01 to 1.0% [00100] Ta, Co, and Sb are elements that contribute to improving the resistance to corrosion by carbon dioxide (CO2 resistance to corrosion), resistance to crack under stress by sulfide and resistance to corrosion and crack under stress by sulfide, and can be contained upon selection, as needed . Cobalt also contributes to raising the point of Ms and increasing resistance. Preferred levels for providing such effects are 0.01% or more for Ta, 0.01% or more for Co, and 0.01% or more for Sb. The effect is not proportional to the content, and becomes saturated when Ta, Co, and Sb are contained in excess of 0.1%, 1.0%, and 1.0%, respectively. For this reason, Ta, Co, and Sb, when contained, are contained in amounts of 0.01 to 0.1%, 0.01 to 1.0%, and 0.01 to 1.0%, respectively.
    [00101] The following description presents the reasons for limiting the structure of the high strength seamless stainless steel tube for tubular petroleum products of the present invention.
    [00102] In addition to the aforementioned composition, the seamless high-strength stainless steel tube for tubular petroleum products of the present invention has a structure that contains more than 45% of the martensite phase (tempered martensite phase) as a primary phase ( basic phase), 10 to 45% ferrite phase and 30% or less austenite phase retained as a secondary phase, by volume.
    [00103] In the seamless steel tube of the present invention, the basic phase is the martensite phase (tempered martensite phase), and the volume fraction of the martensite phase is more than 45% to provide the
    Petition 870190079651, of 16/08/2019, p. 33/58
    23/40 high resistance desired. In the present invention, to provide the desired corrosion resistance (carbon dioxide corrosion resistance, sulfide stress crack resistance (SSC resistance) and sulfide stress corrosion and crack resistance (SCC resistance)), by at least 10 to 45% by volume of a ferrite phase are precipitated as a secondary phase to form a double phase structure of the martensite phase (tempered martensite phase) and the ferrite phase. This forms a laminar structure along the direction of the pipe's geometric axis, and inhibits crack propagation. The laminar structure does not form, and the desired improvement in corrosion resistance cannot be achieved when the ferrite phase is less than 10%. The desired high strength cannot be provided when the ferrite phase is more than 45%, and forms a precipitate in large quantities. For these reasons, the ferrite phase, which is a secondary phase, is 10 to 45%, preferably 20 to 40% by volume.
    [00104] In addition to the ferrite phase as the secondary phase, 30% or less by volume of a retained austenite phase is precipitated. Ductility and toughness improve with the presence of the retained austenite phase. The desired high strength cannot be provided when the retained austenite phase is present in abundance with a volume fraction of more than 30%. Preferably, the retained austenite phase is 5% or more and 30% or less by volume.
    [00105] For the measurement of the structure of the seamless steel tube of the present invention, a test piece for observation of structure is corrected with Vilella's reagent (a mixed reagent containing 2 g of picric acid, 10 ml of hydrochloric acid and 100 ml of ethanol), and the structure is imaged with a scanning electron microscope (magnification: 1000 times). The fraction of the ferrite phase structure (% by volume) is then calculated with an image analyzer.
    [00106] A test piece for X-ray diffraction is crushed and th
    Petition 870190079651, of 16/08/2019, p. 34/58
    24/40 read to provide a measuring cross-sectional surface (cross-section C) orthogonal to the direction of the pipe's geometric axis, and the volume of retained austenite (γ) is measured by x-ray diffractometry. The volume of retained austenite is calculated by measuring the integral x-ray diffraction intensities of the γ plane (220) and the α plane (211) and by converting the results using the following equation.
    γ (volume fraction) = 100 / (1 + (laRy / lyRa)) [00107] In the equation, Ia represents the integral intensity of a, Ra represents a theoretical crystallographic value of α, Ιγ represents the integral intensity of γ, and Ry represents a theoretical crystallographic value of Y · [00108] The fraction of the martensite phase is the fraction except the ferrite phase and the retained austenite phase.
    [00109] In the high strength seamless stainless steel tube for tubular petroleum products of the present invention, ferrite grains have a maximum crystal grain size of 500 pm or less as measured in a 100 mm continuous region inspection 2 supposing that the grains having a crystal orientation difference of not more than 15 ° represent the same grains in electron backscattering diffraction (EBSD): When the ferrite grains have a maximum crystal grain size greater than 500 pm, the desired low temperature toughness cannot be achieved due to the reduced numbers of crystal grain outlines, which interfere with crack propagation. For this reason, the crystal grain size of the steel tube is 500 pm or less in the present invention. The maximum crystal grain size of ferrite grains is preferably 400 pm or less, more preferably 350 pm or less.
    [00110] The maximum crystal grain size can be determined as follows. In an analysis conducted for a contiguous region
    Petition 870190079651, of 16/08/2019, p. 35/58
    25/40 bare 100-mm 2 , grains that have a crystal orientation difference greater than 15 ° are assumed to be the same grains in electron backscattering diffraction (EBSD), and the maximum diameter of the ferrite grains which are supposed to be the same grains is considered to be the crystal grain size of the crystal. The highest value of the crystal grain sizes of all crystals in the 100 mm 2 region can then be determined as the maximum crystal grain size. In the present invention, the maximum crystal grain size of ferrite grains as measured by EBSD can be adjusted to 500 pm or less by heating a steel pipe material before hot working to a heating temperature of 1200 ° C or less, as will be described later.
    [00111] A production method of the high strength seamless stainless steel tube for tubular petroleum products of the present invention is described below, A production method of the high strength seamless stainless steel tube for tubular petroleum products of the present invention includes: heating a steel pipe material to a heating temperature of 1200 ° C or less; working the hot steel pipe material to produce a seamless steel pipe of a predetermined shape; and quench suddenly and quench the seamless steel pipe hot work in succession.
    [00112] A high-strength seamless stainless steel pipe for tubular petroleum products is typically produced by drilling a steel pipe material (for example, a billet) using a pipe production method known, specifically, the method of automatic Mannesmann lamination or the Mannesmann mandrel lamination method. The steel pipe material is heated to a temperature high enough to provide sufficient ductility, as a low temperature of steel pipe material during
    Petition 870190079651, of 16/08/2019, p. 36/58
    26/40 before drilling generally causes defects such as dents, holes and cracks due to low ductility. However, heating to high temperature causes the growth of thick crystals and produces grains of thick crystals in the structure of the final product, with the result that the value of excellent toughness at low temperature cannot be obtained.
    [00113] In the present invention, however, the composition containing more than a certain amount of boron improves hot workability, and grain growth during heating can be reduced without causing defects due to reduced ductility, even if a pipe material steel is heated to a temperature of 1200 ° C or less. This produces a fine structure, and an excellent low temperature toughness value can be obtained.
    [00114] A preferred method of producing a seamless high strength stainless steel tube for tubular petroleum products of the present invention is described below in order, from a starting material. First, a seamless stainless steel tube of the composition described above is used as a starting material in the present invention. The method used to produce the seamless stainless steel pipe from starting material is not particularly limited, except for the heating temperature of the steel pipe material.
    [00115] Preferably, a cast iron of the aforementioned composition is turned into steel using a common steelmaking process using a converter, and formed into steel pipe material, for example, a billet, using a common method as a smelter casting or rolling by ingot decomposition. The steel tube material is heated to a temperature of 1200 ° C, and hot worked using typically a tube manufacturing process known, for example, as
    Petition 870190079651, of 16/08/2019, p. 37/58
    27/40 Mannesmann automatic rolling process, or the Mannermann mandrel rolling mill process to produce a seamless steel tube of the previous composition and in the desired dimensions. Here the growth of thick crystal occurs, and the low temperature toughness of the final product decreases when the heat applied during hot work to improve ductility without causing defects is high. Therefore, it is necessary to make the heating temperature of the steel pipe material 1200 ° C or less, preferably 1180 ° C or less, more preferably 1150 ° C or less. With a heating temperature below 1050 ° C, the workability of the steel material becomes considerably unsatisfactory, it becomes difficult, even with the steel of the present invention, to produce a tube without damaging the outer surface. Therefore, the heating temperature of the steel tube material is preferably 1050 ° C or more, more preferably 1100 ° C or more.
    [00116] After production, the seamless steel pipe is preferably cooled to room temperature at an air-cooling rate or faster. This produces a steel tube structure that has a martensite phase as the basic phase. The seamless steel tube can be produced by hot extrusion by pressing.
    [00117] Here, cooling rate of air cooling or faster means 0.05 ° C / s or more, and room temperature means 40 ° C or less.
    [00118] In the present invention, the cooling of the seamless steel pipe to room temperature at an air-cooling or faster cooling rate followed by sudden cooling, in which the steel pipe is heated to a temperature of 850 ° C or more, and cooled to a temperature of 50 ° C or less at an air-cooled or faster cooling rate. In this way, the
    Petition 870190079651, of 16/08/2019, p. 38/58
    28/40 seamless steel tube can have a structure that has a martensite phase as the basic phase, and the appropriate volume of ferrite phase. Here, air cooling rate or faster means 0.05 ° C / s or more, and room temperature means 40 ° C or less.
    [00119] The desired high resistance cannot be provided when the heating temperature of the sudden cooling is less than 850 ° C. From the point of view of preventing the increase in the size of the structure, the heating temperature of the sudden cooling is preferably 1150 ° C or less. More preferably, the lower limit of the heating temperature of the sudden cooling is 900 ° C, and the upper limit of the heating temperature of the sudden cooling is 1100 ° C.
    [00120] Sudden cooling is followed by quenching, in which the seamless steel tube is heated to a quenching temperature equal to or less than the transformation point Aci and cooled (natural cooling). The quench that heats the steel pipe to a quench temperature equal to or less than the transformation point Aci and cools the steel pipe produces a structure that has a tempered martensite phase, a ferrite phase and a retained austenite phase ( γ phase retained). The product is the high strength seamless stainless steel tube that has the desired high strength, high toughness and excellent corrosion resistance. When the tempering temperature is a high temperature that is above the Aci transformation point, the process produces roughly cooled martensite, and is unable to provide the desired high strength, high toughness and excellent corrosion resistance. Preferably, the tempering temperature is 700 ° C or less, preferably 550 ° C or more.
    EXAMPLES [00121] The present invention is further described through
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    29/40
    Examples.
    [00122] The cast irons of the compositions shown in Table 1 were transformed into steel with a converter, and molded into billets (steel pipe material) by continuous casting. The steel tube material was then heated and hot worked with a seamless rolling machine to produce a seamless steel tube measuring 83.8 mm outside diameter and 12.7 mm wall thickness. This was followed by air cooling. The heating temperature of the steel pipe material before hot work is as shown in Table 2.
    [00123] Each seamless steel tube was cut to obtain a test piece material which was then subjected to sudden cooling, in which the test piece material was heated and cooled under the conditions shown in Table 2. This it was followed by quenching, in which the test piece material was heated and air-cooled under the conditions shown in Table 2.
    [00124] A test piece for observation of the structure was collected from the test piece material abruptly cooled and tempered and corroded with Vilella's reagent (a mixed reagent containing 2 g of picric acid, 10 ml of hydrochloric acid and 100 ml ethanol). The structure was imaged with a scanning electron microscope (magnification: 1000 times), and the fraction of the ferrite phase structure (% by volume) was calculated with an image analyzer.
    [00125] The fraction of the austenite phase structure was measured using x-ray diffractometry. A measurement test piece was collected from the roughly cooled and quenched test piece material, and the integral x-ray diffraction intensities of the γ plane (220) and the α plane (211) were measured by x-ray diffractometry. The results were then converted using the following equation.
    γ (volume fraction) = 100 / (1 + (laRy / lyRa))
    Petition 870190079651, of 16/08/2019, p. 40/58
    30/40 [00126] In the equation, Ια represents the integral intensity of a, Ra represents a theoretical crystallographic value of α, Ιγ represents the integral intensity of γ, and Ry represents a theoretical crystallographic value of T [00127] The phase fraction of martensite was calculated as the different fraction of these phases.
    [00128] In an analysis conducted for a continuous region of 100 mm 2 , it is assumed that the grains that have a difference in crystal orientation greater than 15 ° are the same grains in electron backscattering diffraction (EBSD), and the maximum diameter of the ferrite grains that are assumed to be the same grains is considered to be the crystal grain size of the crystal. The highest value of the crystal grain sizes of all crystals in the 100-mm 2 region was then determined as the maximum crystal grain size.
    [00129] A specimen of strips specified by the API standard was collected from the roughly cooled and quenched test piece material and subjected to a tensile test according to API specifications to determine its tensile characteristics (YS yield strength, strength traction TS). Separately, a V-shaped notch test piece (10 mm thick) was collected from the test piece material abruptly cooled and tempered according to JIS Z 2242 specifications. The test piece was subjected to a Charpy impact, and the absorption energy at -40 ° C was determined for toughness assessment.
    [00130] A corrosion test piece measuring 3.0 mm wall thickness, 30 mm wide and 40 mm long, was machined from the roughly cooled and quenched test piece material and subjected to a corrosion test .
    [00131] The corrosion test was conducted by immersing the test piece for 336 hours in a test solution (an aqueous solution
    Petition 870190079651, of 16/08/2019, p. 41/58
    31/40 s at 20% by weight of NaCI; liquid temperature: 200 ° C, an atmosphere of CO2 gas of 30 atm) charged in an autoclave. After the test, the mass of the test piece was measured and the corrosion rate was determined by reducing the weight calculated before and after the corrosion test. The test piece after the corrosion test was also observed for the presence or absence of alveolar corrosion on a test piece surface using a magnifying glass (10 times magnification). Corrosion with a diameter of 0.2 mm or more was considered to be cellular corrosion.
    [00132] A C-shaped test piece was machined from the roughly cooled and quenched steel tube according to NACE TM0177, Method C, and subjected to an SSC resistance test. The curved surfaces, which correspond to the inner and outer surfaces of the steel tube, have not been ground or polished.
    [00133] A 4 point bending test piece measuring 3 mm thick, 15 mm wide and 115 mm long was collected by machining the test piece material briskly cooled and tempered and subjected to a SCC resistance test and an SSC stress test.
    [00134] In the SCC resistance test (sulfide stress corrosion and cracking), the test piece was immersed in a test solution (an aqueous solution of 20% by weight of NaCI; liquid temperature: 100 ° C; H2S: 0.1 atm; CO2: 30 atm) which has an adjusted pH of 3.3 with the addition of an aqueous solution of acetic acid and sodium acetate in an autoclave. The test piece was kept in the solution for 720 hours to apply a tension equal to 100% of the yield stress. After the test, the test piece was observed for the presence or absence of cracking.
    [00135] In the SSC resistance test (sulfide stress crack), the test piece was immersed in a test solution (a single solution)
    Petition 870190079651, of 16/08/2019, p. 42/58
    32/40 aqueous solution of 20% by weight of NaCI; liquid temperature: 25 ° C; H2S: 0.1 atm; CO2: 0.9 atm) which has an adjusted pH of 3.5 with the addition of an aqueous solution of acetic acid and sodium acetate, the test piece was kept in the solution for 720 hours to apply a voltage equal to 90% the yield stress.
    [00136] The results are shown in Table 2.
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    Table 1
    Steel No. Composition (% by mass) Value on the left side of the formula (1) (* 1) Value on the left side of the formula (2) (* 2) Ç Si Mn P s Cr Ni Mo Ass W V Al N B Nb, Ti, Zr REM, Ca, Sn, Mg Ta, Co, Sb THE 0.012 0.30 0.26 0.013 0.0009 15.1 4.8 4.0 2.5 1.1 0.048 0.017 0.011 0.0041 - - - 27.3 32.3 B 0.009 0.28 0.28 0.016 0.0008 15.3 4.9 3.6 2.5 1.1 0.052 0.025 0.011 0.0025 - - - 25.6 32.3 Ç 0.017 0.26 0.28 0.014 0.0008 15.1 4.8 3.0 2.5 1.2 0.048 0.022 0.014 0.0087 - - - 19.7 31.4 D 0.011 0.21 0.24 0.015 0.0008 15.0 4.5 3.1 2.5 1.1 0.047 0.021 0.008 0.0061 - - - 22.7 30.7 AND 0.013 0.26 0.25 0.015 0.0010 15.1 4.7 4.3 2.6 1.3 0.050 0.021 0.012 0.0025 Nb: 0.145 - - 29.2 32.6 F 0.015 0.24 0.28 0.016 0.0012 14.9 4.6 4.3 2.6 1.2 0.047 0.023 0.013 0.0036 - - - 28.4 32.2 G 0.010 0.23 0.29 0.014 0.0011 15.5 3.7 3.1 2.8 1.1 0.051 0.021 0.004 0.0023 - - - 30.2 29.9 H 0.012 0.25 0.29 0.015 0.0009 15.0 3.8 3.0 2.6 1.3 0.054 0.023 0.004 0.0019 - - - 26.3 29.5 1 0.033 0.27 0.24 0.015 0.0010 15.2 3.9 3.3 2.6 0.9 0.050 0.023 0.062 0.0052 Nb: 0.056 - - 21.8 29.8 J 0.005 0.29 0.28 0.016 0.0007 15.2 4.3 3.5 2.7 1.2 0.041 0.023 0.014 0.0048 - REM: 0.021, Ca: 0.0021 - 28.2 31.2 K 0.010 0.22 0.26 0.015 0.0007 14.9 4.2 3.6 2.5 1.1 0.047 0.023 0.014 0.0034 - - Ta: 0.02, Co: 0.24 27.0 30.5 L 0.006 0.24 0.22 0.015 0.0009 15.1 4.3 3.2 2.3 1.3 0.044 0.028 0.012 0.0029 Ti: 0.054, Zr: 0.10 Sn: 0.13, Mg: 0.0007 - 26.0 30.5 M 0.006 0.26 0.21 0.014 0.0008 14.8 4.6 3.4 2.4 1.5 0.046 0.021 0.013 0.0028 Ti: 0.046 - Sb: 0.14 24.1 31.2
    33/40
    Petition 870190079651, of 16/08/2019, p. 44/58
    SteelAt the. Composition (% by mass) Value on the left side of the formula (1) (* 1) Value on the left side of the formula (2) (* 2) Ç Si Mn P s Cr Ni Mo Ass W V Al N B Nb, Ti, Zr REM,Ca, Sn, Mg Ta, Co,Sb N 0.006 0.23 0.23 0.020 0.0007 14.9 4.6 3.5 2.4 1.2 0.042 0.024 0.015 0.0010 - Ca: 0.0020, Mg: 0.0009 Ta: 0.02, Sb: 0.12 24.7 31.2 O 0.009 0.21 0.29 0.019 0.0007 15.1 4.7 3.4 2.5 1.5 0.044 0.011 0.014 0.0040 Zr: 0.08 REM: 0.021, Sn: 0.11 Co: 0.26 23.9 31.9 P 0.015 0.28 0.29 0.014 0.0009 15.1 5.6 3.5 2.4 1.3 0.049 0.030 0.009 0.0050 - - - 19.1 33.5 Q 0.015 0.29 0.21 0.013 0.0011 15.7 3.6 3.0 3.3 0.8 0.044 0.019 0.036 0.0037 - - - 28.1 30.0 R 0.014 0.27 0.23 0.012 0.0009 15.6 3.4 2.9 2.6 1.5 0.134 0.024 0.014 0.0045 - - - 30.4 29.4 s 0.037 0.25 0.35 0.016 0.0009 16.8 3.5 2.8 0.8 1.3 0.059 0.027 0.012 0.0028 Nb: 0.069 - - 33.9 28.7 T 0.015 0.22 0.31 0.011 0.0010 15.6 3.7 2.9 2.8 0.9 0.061 0.023 0.044 0.0026 - - - 25.9 29.6
    34/40. The balance is Fe and unavoidable impurities (* 1) Value on the left side of the formula (1) = -5.9x (7.82 + 27C-0.91Si + 0.21Mn-0.9Cr + Ni-1.1Mo + 0.2Cu + 11N) (In the formula, C, Si, Mn, Cr, Ni, Mo, Cu, and N represent the content of each element (mass%)) (* 2) Value on the left side of the formula (2 ) = Cu + Mo + W + Cr + 2Ni (In the formula, Cu, Mo, W, Cr, and Ni represent the content of each element (mass%). The underline means outside the range of the present invention.
    Petition 870190079651, of 16/08/2019, p. 45/58 [Tabe a 1] Continued
    Steel No. Composition (% by mass) Value on the left side of the formula (1) (* 1) Value on the left side of the formula (2) (* 2) Ç Si Mn P s Cr Ni Mo Ass W V Al N B Nb, Ti, Zr REM, Ca, Sn, Mg Ta, Co, Sb U 0.012 0.24 0.30 0.014 0.0009 16.1 4.1 4.1 2.5 1.2 0.041 0.025 0.016 0.0027 - - - 37.9 32.1 V 0.012 0.21 0.29 0.014 0.0010 14.83.1 2.5 0.9 0.055 0.022 0.014 0.0029 - - - 32.9 26.3 W 0.033 0.27 0.29 0.014 0.0010 16.2 3.8 £ 3 1.1 1.0 0.058 0.038 0.047 0.0046 - - - 23.8 28.2 X 0.027 0.22 0.30 0.014 0.0013 17.8 3.6 3.0 1.3 1.1 0.053 0.041 0.048 0.0038 - - - 38.5 30.4 Y 0.011 0.25 0.26 0.014 0.0009 14.8 6.2 3.6 2.6 1.0 0.061 0.019 0.009 0.0051 - - - 14.8 34.4 z 0.012 0.26 0.27 0.012 0.0009 14.8 3.8 L5 2.4 1.1 0.054 0.018 0.009 0.0041 - - - 41.5 31.4 AA 0.012 0.23 0.26 0.015 0.0010 15.5 3.6 3.1 £ 4 1.1 0.058 0.019 0.009 0.0011 - - - 28.4 31.2 AB 0.012 0.23 0.29 0.016 0.0008 14.2 3.2 2.9 2.6 0.9 0.052 0.021 0.014 0.0029 - - - 24.2 27.0 B.C 0.031 0.21 0.35 0.014 0.0014 16.3 3.6 2.9 0J. 1.0 0.049 0.032 0.056 0.0030 - - - 30.0 27.5 AD 0.028 0.25 0.31 0.015 0.0009 16.8 4.1 3.0 2.7 1.0 0.012 0.034 0.043 0.0035 - - - 28.9 31.7 AE 0.033 0.22 0.33 0.016 0.0010 16.1 3.4 2.9 2.7 - 0.059 0.044 0.041 0.0049 - - - 27.8 28.5 AF 0.013 0.22 0.30 0.014 0.0010 15.9 4.0 3.0 2.6 1.0 0.112 0.028 0.028 0.0150 - - - 28.0 29.5 AG 0.020 0.21 0.26 0.018 0.0012 17.2 4.1 3.1 2.5 1.4 0.059 0.029 0.022 0.0003 - - - 34.4 31.0 AH 0.009 0.23 0.33 0.019 0.0006 14.9 5.8 3.3 2.6 0.9 0.081 0.024 0.070 0.0053 - - - 12.0 33.3 Δ1 0.025 0.21 0.31 0.018 0.0006 17.1 5.7 3.4 2.4 1.6 0.056 0.044 0.012 0.0020 - - - 26.2 35.9 AJ 0.009 0.27 0.31 0.016 0.0009 15.9 4.0 3.1 2.6 1.3 0.053 0.026 0.023 0.0026 - - - 29.9 30.9 AK 0.012 0.56 0.26 0.013 0.0009 15.1 4.8 4.0 2.5 1.1 0.048 0.017 0.011 0.0041 - - - 28.7 32.3 AL 0.012 0.30 1.10 0.013 0.0009 15.1 4.8 4.0 2.5 1.1 0.048 0.017 0.011 0.0041 - - - 26.3 32.3 AM 0.012 0.30 0.14 0.013 0.0009 15.1 4.8 4.0 2.5 1.1 0.048 0.017 0.011 0.0041 - - - 27.5 32.3 AN 0.012 0.30 0.26 0.013 0.0009 14.4 4.8 4.0 2.5 1.1 0.048 0.017 0.011 0.0041 - - - 23.6 31.6 TO 0.012 0.30 0.26 0.013 0.0009 15.1 £ 2 4.0 2.5 1.1 0.048 0.017 0.011 0.0041 - - - 38.6 28.5 AP 0.012 0.30 0.26 0.013 0.0009 15.1 4.8 £ 2 2.5 1.1 0.048 0.017 0.011 0.0041 - - - 18.3 30.9
    . The balance is Fe and unavoidable impurities (* 1) Value on the left side of the formula (1) = -5.9x (7.82 + 27C-0.91Si + 0.21Mn-0.9Cr + Ni-1.1Mo + 0.2Cu + 11N) (In the formula, C, Si, Mn, Cr, Ni, Mo, Cu, and N represent the content of each element (mass%)) (* 2) Value on the left side of the formula (2 ) = Cu + Mo + W + Cr + 2Ni (In the formula, Cu, Mo, W, Cr, and Ni represent the content of each element (mass%). The underline means outside the range of the present invention.
    35/40
    Petition 870190079651, of 16/08/2019, p. 46/58
    Table 21
    Steel No. No. steel tube Heating temperature of steel pipe material (° C) Sudden cooling Hardening Structure (% by volume) Maximum crystal grain size of ferrite grains (pm) (* 2) YS flow resistance (MPa) Tensile strength TS (MPa) vE-40(J) Corrosion rate (mm / y) Alveolar corrosion SSC scc Comments Heating temperature (° C) Retention time (min) Heating temperature (° C) Retention time (min) M (* 1) F (* 1) TO 1) THE 1 1180 1050 20 575 30 61 31 8 289 977 1052 154 0.033 Absent O O Present Example B 2 1180 1030 20 575 30 65 30 5 267 952 1012 156 0.035 Absent O O Present Example Ç 3 1180 1000 20 565 30 67 29 4 244 963 1013 186 0.035 Absent O O Present Example D 4 1180 1000 20 565 30 61 34 5 239 969 1018 130 0.029 Absent O O Present Example AND 5 1150 1050 20 570 30 49 43 8 296 954 1066 105 0.033 Absent O O Present Example F 6 1150 1050 20 570 30 58 35 7 294 948 1082 122 0.044 Absent O O Present Example G 7 1150 980 20 590 30 67 31 2 260 886 953 152 0.036 Absent O O Present Example H 8 1150 1000 20 560 30 66 32 2 279 968 1028 156 0.027 Absent O O Present Example 1 9 1150 980 20 580 30 64 30 6 265 958 1135 147 0.050 Absent O O Present Example J 10 1180 1030 20 575 30 66 29 5 266 970 1024 126 0.036 Absent O O Present Example K 11 1180 1030 20 575 30 65 30 5 260 972 1018 160 0.032 Absent O O Present Example L 12 1180 1010 20 575 30 65 32 3 249 964 1018 172 0.025 Absent O O Present Example M 13 1180 1030 20 575 30 68 29 3 266 926 1021 171 0.045 Absent O O Present Example N 14 1180 1030 20 575 30 64 32 4 271 970 1009 153 0.033 Absent O O Present Example O 15 1180 1030 20 575 30 62 32 6 273 950 1030 186 0.028 Absent O O Present Example P 16 1150 1050 20 575 30 64 25 11 288 916 1062 175 0.031 Absent O O Present Example Q 17 1150 980 20 590 30 72 26 2 270 931 1053 123 0.031 Absent O O Present Example R 18 1150 1000 20 560 30 66 31 3 276 934 1034 110 0.027 Absent O O Present Example s 19 1150 970 20 560 30 56 38 6 261 920 1055 117 0.019 Absent O O Present Example T 20 1150 980 20 590 30 64 36 0 265 958 1007 107 0.034 Absent O O Present Example
    (* 1) M: Martensitic phase, F: Ferritic phase, A: Retained austenitic phase (* 2) Maximum crystal grain size of ferrite grains as measured in a 100 mm 2 continuous region inspection assuming that the grains having a crystal orientation difference of no more than 15 ° represent the same grains in electron backscattering diffraction (EBSD):. The underline means outside the range of the present invention.
    36/40
    Petition 870190079651, of 16/08/2019, p. 47/58 [Table 2] Continuation
    Steel No. No. steel tube Heating temperature of steel pipe material (° C) Sudden cooling Hardening Structure (% by volume) Maximum crystal grain size of ferrite grains (pm) (* 2) YS flow resistance (MPa) Tensile strength TS (MPa) vE-40(J) Corrosion rate (mm / y) Alveolar corrosion SSC SCC Comments Heating temperature (° C) Retention time (min) Heating temperature (° C) Retention time (min) M (* 1) F (* 1) TO 1) W 23 1180 970 20 560 30 65 30 5 266 862 1016 106 0.030 Absent X X Comparative example X 24 1180 970 20 560 30 50 46 4 263 842 1023 32 0.010 Absent O O Comparative example Y 25 1150 1050 20 575 30 49 21 20 258 850 1039 230 0.030 Absent O O Comparative example z 26 1150 1080 20 580 30 54 36 10 270 912 1043 30 0.030 Gift X X Comparative example AA 27 1150 980 20 590 30 59 35 6 249 916 1017 131 0.038 Absent X X Comparative example AB 28 1150 960 20 570 30 65 35 0 246 942 1020 115 0.139 Gift X X Comparative example B.C 29 1180 970 20 555 30 64 33 3 271 936 1019 123 0.027 Absent X X Comparative example AD 30 1180 970 20 560 30 62 30 8 263 854 1058 122 0.016 Absent O O Comparative example AE 31 1180 970 20 560 30 67 32 1 270 847 1048 157 0.041 Gift X X Comparative example AF 32 1180 1000 20 595 30 60 31 9 277 901 1015 51 0.019 Absent O O Comparative example AG 33 1180 1040 20 550 30 58 27 15 324 886 981 111 0.046 Absent X O Comparative example AJ 36 1230 1000 20 575 30 60 22 18 518 870 998 42 0.011 Absent O O Comparative example AK 37 1180 960 20 570 30 65 25 10 264 888 1001 121 0.078 Absent X O Comparative example AL 38 1180 960 20 570 30 67 24 9 257 901 1012 60 0.058 Absent O O Comparative example AM 39 1180 960 20 570 30 65 25 10 251 845 931 109 0.061 Absent O O Comparative example AN 40 1180 960 20 570 30 65 26 9 270 920 1055 117 0.153 Gift X X Comparative example TO 41 1180 960 20 570 30 68 23 9 266 832 945 108 0.132 Absent X X Comparative example AP 42 1180 960 20 570 30 67 24 9 260 916 1062 175 0.098 Absent X X Comparative example
    (* 1) M: Martensitic phase, F: Ferritic phase, A: Retained austenitic phase (* 2) Maximum crystal grain size of ferrite grains as measured in a 100 mm 2 continuous region inspection assuming that the grains having a crystal orientation difference of no more than 15 ° represent the same grains in electron backscattering diffraction (EBSD):. The underline means outside the range of the present invention.
    37/40
    Petition 870190079651, of 16/08/2019, p. 48/58
    38/40 [00137] All the high strength stainless steel tubes in the present examples had high strength with a yield strength of 862 MPa or more, high toughness with an absorption energy at -40 ° C of 100 J or more, and excellent corrosion resistance (corrosion resistance by carbon dioxide) in a high temperature corrosive environment containing CO2 and Cl · at 200 ° C. The high strength seamless stainless steel tubes of the present examples did not produce cracking (SSC, SCC) in the H2S-containing environment, and had excellent resistance to cracking under sulfide stress and excellent resistance to corrosion and cracking under tension by sulfide.
    [00138] On the other hand, the comparative examples outside the range of the present invention did not have at least one among the high strength, low temperature toughness, resistance to corrosion by carbon dioxide, resistance to crack under stress by sulfide (resistance to SSC ) and sulfide corrosion resistance (SCC resistance).
    [00139] Steel tube No. 23 (steel No. W) had a Mo content of less than 2.7%, by weight, and the desired SSC and SCC resistance were not achieved.
    [00140] Steel tube No. 24 (steel No. X) had a Cr content greater than 17.5%, by weight, and the ferrite phase exceeded 45%. YS flow resistance was less than 862 MPa, and 0 vE-40 was less than 100 J.
    [00141] No. 25 steel tube (No. Y steel) had a Ni content greater than 6.0%, by weight, and YS flow resistance was less than 862 MPa.
    [00142] Steel tube No. 26 (steel No. Z) had a Mo content greater than 5.0%, by weight, and 0 vE-40 was less than 100 J. As a result, alveolar corrosion occurred, and the desired SSC resistance and SCC resistance have not been obtained.
    Petition 870190079651, of 16/08/2019, p. 49/58
    39/40 [00143] Steel tube No. 27 (steel No. AA) had a Cu content greater than 4.0%, by weight, and the desired SSC resistance and SCC resistance were not obtained.
    [00144] Steel tube No. 28 (steel No. AB) had a Cr content less than 14.5% by weight. As a result, honeycomb corrosion occurred, and the desired SSC and SCC resistance were not achieved.
    [00145] Steel tube No. 29 (steel No. AC) had a Cu content of less than 0.3%, by weight, and the desired SSC and SCC resistance were not achieved.
    [00146] Steel tube No. 30 (steel No. AD) had a V content of less than 0.02%, by weight, and YS flow resistance was less than 862 MPa.
    [00147] Steel tube No. 31 (steel No. AE) had a W content of less than 0.1%, by weight, and the yield strength YS was less than 862 MPa. As a result, honeycomb corrosion occurred, and the desired SSC and SCC resistance were not achieved.
    [00148] Steel tube No. 32 (steel No. AF) had a B content greater than 0.0100%, by weight, and the vE-40 was less than 100 J.
    [00149] Steel tube No. 33 (steel No. AG) had a B content of less than 0.0005% by weight and the hot workability was insufficient. As a result, damage occurred during tube manufacture, and the desired SSC resistance was not achieved.
    [00150] Steel tube No. 36 had a heating temperature of over 1200 ° C. The maximum crystal grain size of ferrite grains exceeded 500 pm, and the vE-40 was less than 100 J.
    [00151] Steel tube No. 37 had a Si content greater than 0.5%, by weight, and hot workability was insufficient. As a result, damage occurred during tube manufacture, and the desired SSC resistance was not achieved.
    Petition 870190079651, of 16/08/2019, p. 50/58
    40/40 [00152] Steel tube No. 38 had an Mn content greater than 1.0%, by weight, and the vE-40 was less than 100 J.
    [00153] Steel tube No. 39 had an Mn content less than 0.15%, by weight, and the YS flow resistance was less than 862 MPa.
    [00154] Steel tube No. 40 had a Cr content less than 14.5% by weight and the desired carbon dioxide corrosion resistance, the desired honeycomb resistance and the desired SSC and SCC resistance were not obtained.
    [00155] Steel tube No. 41 had a Ni content of less than 3.0%, by weight. The YS flow resistance was less than 862 MPa, and the desired carbon dioxide corrosion resistance, the desired honeycomb resistance and the desired SSC and SCC resistance were not obtained.
    [00156] Steel tube No. 42 had a Mo content of less than 2.7%, by weight, and the desired SSC and SCC strengths were not achieved.
    权利要求:
    Claims (5)
    [1]
    1. High strength seamless stainless steel tube for tubular petroleum products, characterized by the fact that the high strength seamless stainless steel tube has a flow resistance of 862 MPa or more with a composition that comprises, in%, by weight, C: 0.05% or less, Si: 0.5% or less, Mn: 0.15 to 1.0%, P: 0.030% or less, S: 0.005% or less, Cr: 14, 5 to 17.5%, Ni: 3.0 to 6.0%, Mo: 2.7 to 5.0%, Cu: 0.3 to 4.0%, W: 0.1 to 2.5% , V: 0.02 to 0.20%, Al: 0.10% or less, N: 0.15% or less, B: 0.0005 to 0.0100%, and the balance is Fe and unavoidable impurities, and where C, Si, Mn, Cr, Ni, Mo, Cu, and N satisfy formula (1) below, and Cu, Mo, W, Cr and Ni satisfy formula (2) below, where stainless steel tube has a structure that contains more than 45% martensite phase as a primary phase, 10 to 45% ferrite phase and 30% or less retained austenite phase as a secondary phase, by volume, and in which ferrite grains have a crystal grain size maximum 500 pm or less as measured in an inspection of a continuous 100 mm 2 region assuming that the grains having a crystal orientation difference of no more than 15 ° represent the same grains in electron backscattering diffraction (EBSD): Formula (1)
    -5.9 x (7.82 + 27C - 0.91 Si + 0.21 Mn - 0.9Cr + Ni - 1.1 Mo + 0.2Cu + 11N)> 13.0, where C, Si, Mn, Cr, Ni, Mo, Cu, and N represent the content of each element (% by mass); and
    Formula (2)
    Cu + Mo + W + Cr + 2Ni <34.5, where Cu, Mo, W, Cr, and Ni represent the content of each element (% by mass).
    Petition 870190079651, of 16/08/2019, p. 52/58
    [2]
    2/2
    2. High-strength seamless stainless steel tube for tubular petroleum products, according to claim 1, characterized by the fact that the composition additionally comprises, in% by weight, at least one selected from Nb: 0, 02 to 0.50%, Ti: 0.02 to 0.16%, and Zr: 0.02 to 0.50%.
    [3]
    3. High-strength seamless stainless steel tube for tubular petroleum products, according to claim 1 or 2, characterized by the fact that the composition additionally comprises, in% by weight, at least one selected from REM: 0.001 to 0.05%, Ca: 0.001 to 0.005%, Sn: 0.05 to 0.20%, and Mg: 0.0002 to 0.01%.
    [4]
    4. High-strength seamless stainless steel tube for tubular petroleum products according to any one of claims 1 to 3, characterized in that the composition additionally comprises, in% by weight, at least one selected from Ta: 0.01 to 0.1%, Co: 0.01 to 1.0%, and Sb: 0.01 to 1.0%.
    [5]
    5. Production method of the seamless high-strength stainless steel tube for tubular petroleum products, as defined in any of claims 1 to 4, characterized by the fact that the method comprises: heating a steel tube material to a temperature heating temperature of 1200 ° C or less;
    working the hot steel pipe material to produce a seamless steel pipe of a predetermined shape; and cool down sharply and temper the hot-worked seamless steel pipe in succession.
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    WO2018131340A1|2017-01-13|2018-07-19|Ｊｆｅスチール株式会社|High strength seamless stainless steel pipe and production method therefor|
    KR102337567B1|2017-05-26|2021-12-08|제이에프이 스틸 가부시키가이샤|Ferritic stainless steel|
    EP3916120A4|2019-03-29|2022-02-16|Jfe Steel Corp|Stainless seamless steel pipe|
    WO2021187331A1|2020-03-19|2021-09-23|Ｊｆｅスチール株式会社|Stainless seamless steel pipe and method for producing stainless seamless steel pipe|
    WO2021187330A1|2020-03-19|2021-09-23|Ｊｆｅスチール株式会社|Stainless seamless steel pipe and method for producing stainless seamless steel pipe|
    法律状态:
    2021-10-19| B350| Update of information on the portal [chapter 15.35 patent gazette]|
    优先权:
    申请号 | 申请日 | 专利标题
    JP2017033009|2017-02-24|
    PCT/JP2018/001868|WO2018155041A1|2017-02-24|2018-01-23|High strength seamless stainless steel pipe for oil well and production method therefor|
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