Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
  • C21D9/085—Cooling or quenching
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
  • C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/008—Martensite

Definitions

• the present invention relates to a martensitic stainless steel seamless pipe for use in oil country tubular goods used in oil well and gas well applications such as in crude oil wells and natural gas wells, and to a method for producing such a martensitic stainless steel seamless pipe.
• the invention particularly relates to improvement of corrosion resistance in a severe corrosive environment containing carbon dioxide gas (CO 2 ), chlorine ions (Cl - ), and the like, and improvement of sulfide stress corrosion cracking resistance (SSC resistance) in a hydrogen sulfide (H 2 S)-containing environment.
• Oil country tubular goods used for mining of oil fields and gas fields of an environment containing CO 2 gas, Cl - , and the like often use 13% Cr martensitic stainless steel pipes.
• 13% Cr martensitic stainless steel pipes In order to meet the increasing demand for higher SSC resistance arising out of the world-wide development of oil fields of a severe corrosive environment containing hydrogen sulfide, there has been increasing use of modified 13% Cr martensitic stainless steel pipes containing a reduced carbon content, and increased Ni and Mo contents.
• PTL 1 discloses a 13% Cr steel basic composition containing Ni, Mo, and Cu, and a much smaller carbon content than in traditional compositions. These elements are contained to satisfy Cr + 2Ni + 1.1Mo + 0.7Cu ⁇ 32.5, and Nb + V ⁇ 0.05% for at least one of Nb: 0.20% or less, and V: 0.20% or less.
• the composition is described as being capable of providing high strength with a yield strength of 965 MPa or more, and high toughness with a Charpy absorption energy at -40°C of 50 J or more, in addition to desirable corrosion resistance.
• PTL 2 describes a 13% Cr martensitic stainless steel pipe having an extremely low carbon content of 0.015% or less, and a Ti content of 0.03% or more. With such a composition, the 13% Cr martensitic stainless steel pipe can have high strength with a yield stress in the order of 95 ksi (655 to 758 MPa), low hardness with a Rockwell hardness HRC of less than 27, and excellent SSC resistance.
• PTL 3 describes a martensitic stainless steel that satisfies 6.0 ⁇ Ti/C ⁇ 10.1, where Ti/C has a correlation with a value obtained by subtracting the yield stress from the tensile stress. The technique described in this publication can produce a value of 20.7 MPa or more as the difference of the yield stress from the tensile stress, and can reduce the hardness variation, which deteriorates the SSC resistance.
• PTL 4 describes a martensitic stainless steel containing a specified amount of molybdenum satisfying Mo ⁇ 2.3-0.89Si + 32.2C, and having a metal structure that is configured primarily from tempered martensite, carbides that have precipitated during tempering, and intermetallic compounds, such as the Laves phase and the ⁇ phase, that have finely precipitated during tempering.
• the technique described in this publication can achieve high strength with a 0.2% proof stress of 860 MPa or more, and excellent carbon dioxide corrosion resistance, and excellent sulfide stress corrosion cracking resistance.
• Recent oil fields and gas fields are developed in severe corrosive environments containing CO 2 , Cl - , and H 2 S. There are also rising concerns over increased H 2 S concentrations due to aging.
• the oil country tubular goods used in these environments are thus required to have excellent sulfide stress corrosion cracking resistance (SSC resistance), in addition to carbon dioxide corrosion resistance.
• SSC resistance sulfide stress corrosion cracking resistance
• the technique of PTL 1 is described as providing excellent carbon dioxide corrosion resistance.
• the technique cannot be said as providing the level of corrosion resistance that can withstand a severe corrosive environment.
• PTL 2 sulfide stress corrosion cracking resistance can be maintained under an applied stress of 655 MPa in an atmosphere of a 5% NaCl aqueous solution (H 2 S: 0.10 bar) with an adjusted pH of 3.5.
• PTL 3 describes providing sulfide stress corrosion cracking resistance in an atmosphere of a 20% NaCl aqueous solution (H 2 S: 0.03 atm, CO 2 balance.) with an adjusted pH of 4.5.
• PTL 4 describes providing sulfide stress corrosion cracking resistance in an atmosphere of a 25% NaCl aqueous solution (H 2 S: 0.003 MPa, CO 2 balance.) with an adjusted pH of 4.0.
• these techniques do not investigate sulfide stress corrosion cracking resistance in other atmospheres, and cannot be said as providing the level of sulfide stress corrosion cracking resistance that can withstand the today's more severe corrosive environments.
• the invention is also intended to provide a method for producing such a martensitic stainless steel seamless pipe for oil country tubular goods.
• high-strength means a yield stress of 758 MPa (110 ksi) or more.
• the yield stress is 896 MPa or less.
• excellent sulfide stress corrosion cracking resistance means that a test piece dipped in a test solution (a 0.165 mass% NaCl aqueous solution; liquid temperature: 25°C, H 2 S: 1 bar, CO 2 balance) having an adjusted pH of 3.5 with addition of sodium acetate and hydrochloric acid does not crack even after 720 hours under an applied stress equal to 90% of the yield stress.
• a test solution a 0.165 mass% NaCl aqueous solution; liquid temperature: 25°C, H 2 S: 1 bar, CO 2 balance
• the present inventors conducted intensive studies of various alloy elements in a basic composition of a 13% Cr stainless steel pipe with regard to the effects of these elements on sulfide stress corrosion cracking resistance (SSC resistance) in a corrosive environment containing CO 2 , Cl - , and H 2 S.
• SSC resistance sulfide stress corrosion cracking resistance
• a martensitic stainless steel seamless pipe for oil country tubular goods having the desired strength, and excellent SSC resistance in a CO 2 -, Cl - -, and H 2 S-containing corrosive environment under an applied stress close to the yield stress can be produced when a composition containing C, Mn, Cr, Cu, Ni, Mo, W, Nb, N, and Ti in adjusted amounts that satisfy appropriate relations and ranges is subjected to appropriate quenching and tempering treatments.
• the present invention can produce a martensitic stainless steel seamless pipe for oil country tubular goods having excellent sulfide stress corrosion cracking resistance (SSC resistance) in a CO 2 -, Cl - -, and H 2 S-containing corrosive environment, and high strength with a yield stress YS of 758 MPa (110 ksi) or more.
• SSC resistance sulfide stress corrosion cracking resistance
• a seamless stainless steel pipe of the present invention is a martensitic stainless steel seamless pipe for oil country tubular goods.
• the martensitic stainless steel seamless pipe has a composition that contains, in mass%, C: 0.035% or less, Si: 0.5% or less, Mn: 0.05 to 0.5%, P: 0.03% or less, S: 0.005% or less, Cu: 2.6% or less, Ni: 5.3 to 7.3%, Cr: 11.8 to 14.5%, Al: 0.1% or less, Mo: 1.8 to 3.0%, V: 0.2% or less, N: 0.1% or less, and the balance Fe and unavoidable impurities, and that satisfies the following formula (4), (5), or (6) with the following formulae (1), (2), and (3).
• the martensitic stainless steel seamless pipe has a yield stress of 758 MPa or more.
• C, Mn, Cr, Cu, Ni, Mo, W, Nb, N, and Ti represent the content of each element in mass% (the content being 0 (zero) percent for elements that are not contained).
• composition of the steel pipe of the present invention is as follows .
• “%” means percent by mass, unless otherwise specifically stated.
• Carbon is an important element involved in the strength of the martensitic stainless steel, and effectively improves the strength.
• a carbon content of more than 0.035% makes the hardness excessively high, and increases the sensitivity to sulfide stress corrosion cracking.
• the C content is limited to 0.035% or less in the present invention.
• the C content is 0.015% or less. More preferably, the C content is 0.0090% or less. Further preferably, the C content is 0.0075% or less. Desirably, carbon is contained in an amount of 0.005% or more to provide the desired strength.
• Silicon acts as a deoxidizing agent, and should be contained in an amount of 0.05% or more.
• a Si content of more than 0.5% deteriorates carbon dioxide corrosion resistance and hot workability. For this reason, the Si content is limited to 0.5% or less.
• the lower limit of Si content is preferably 0.10% or more, and the upper limit of Si content is preferably 0.30% or less.
• Manganese is an element that improves hot workability, and is contained in an amount of 0.05% or more. When contained in excess of 0.5%, the effect becomes saturated, and this leads to increased cost. For this reason, the Mn content is limited to 0.05 to 0.5%. Preferably, the Mn content is 0.40% or less.
• Phosphorus is an element that deteriorates carbon dioxide corrosion resistance, pitting corrosion resistance, and sulfide stress corrosion cracking resistance, and should be contained in as small an amount as possible in the present invention.
• an excessively small P content leads to increased manufacturing cost.
• the P content is therefore limited to 0.03% or less, a content that does not bring about an excessive loss of characteristics, and that is industrially feasible in terms of cost.
• the P content is 0.02% or less.
• Sulfur is an element that seriously deteriorates hot workability, and should desirably be contained in as small an amount as possible.
• a S content of 0.005% or less enables pipe production using common procedures, and accordingly the S content is limited to 0.005% or less in the present invention.
• the S content is 0.003% or less.
• Copper adds strength to the protective coating, and improves sulfide stress corrosion cracking resistance.
• a Cu content of more than 2.6% causes precipitation of CuS, and deteriorates hot workability.
• the Cu content is limited to 2.6% or less.
• the lower limit of Cu content is preferably 0.5% or more, and the upper limit of Cu content is preferably 2.0% or less.
• nickel When contained in an amount of 5.3% or more, nickel adds strength to the protective coating, and improves corrosion resistance. Nickel also forms a solid solution, and increases the steel strength in this content range. A Ni content of more than 7.3% makes the martensite phase unstable, and the strength deteriorates. For this reason, the Ni content is limited to 5.3 to 7.3%. Preferably, the Ni content is 5.7% or more, more preferably 6.0% or more.
• Chromium is an element that forms a protective coating, and improves the corrosion resistance. Chromium provides the corrosion resistance necessary for oil country tubular goods applications when contained in an amount of 11.8% or more. A Cr content or more than 14.5% facilitates ferrite generation, and the martensite phase cannot remain stable. For this reason, the Cr content is limited to 11.8 to 14.5%.
• the lower limit of Cr content is preferably 12.0% or more, and the upper limit of Cr content is preferably 13.5% or less.
• Aluminum acts as a deoxidizing agent.
• An Al content of 0.01% or more effectively provides this effect. Because an Al content of more than 0.1% adversely affects toughness, the Al content is limited to 0.1% or less in the present invention. Preferably, the Al content is 0.01 to 0.03%.
• Molybdenum is an element that improves the pitting corrosion resistance caused by Cl - . Molybdenum needs to be contained in an amount of 1.8% or more to obtain the corrosion resistance necessary for a severe corrosive environment. The effect becomes saturated when the Mo content is more than 3.0%. Molybdenum is also an expensive element, and increases the manufacturing cost. For these reasons, the Mo content is limited to 1.8 to 3.0%.
• the lower limit of Mo content is preferably 2.4% or more, and the upper limit of Mo content is preferably 2.9% or less.
• Vanadium is contained in an amount of desirably 0.01% or more, in order to improve steel strength by precipitation strengthening, and to improve sulfide stress corrosion cracking resistance.
• a V content of more than 0.2% deteriorates toughness, and the V content is limited to 0.2% or less in the present invention.
• the lower limit of V content is preferably 0.01% or more, and the upper limit of V content is preferably 0.08% or less.
• Nitrogen is an element that greatly improves the pitting corrosion resistance.
• a N content of more than 0.1% causes formation of various nitrides, and deteriorates toughness.
• the N content is limited to 0.1% or less in the present invention.
• the N content is 0.003% or more.
• the lower limit of N content is more preferably 0.004% or more, further preferably 0.005% or more.
• the upper limit of N content is more preferably 0.08% or less, further preferably 0.05% or less.
• Formula (1) is a formula that correlates with the residual ⁇ amount. By making the calculated value of formula (1) smaller, the residual austenite is reduced, and the hardness reduces, with the result that the sulfide stress corrosion cracking resistance improves.
• Formula (2) is a formula that correlates with the repassivation potential.
• Regeneration of the passivation coating occurs more easily, and repassivation improves by containing C, Mn, Cr, Cu, Ni, Mo, W, Nb, N, and Ti in such amounts that formula (1) yields a value that satisfies the range of formula (4), (5), or (6), and by containing Mn, Cr, Cu, Ni, Mo, W, N, and Ti in such amounts that formula (2) yields a value that satisfies the range of formula (4), (5), or (6).
• Formula (3) is a formula that correlates with the pitting corrosion potential.
• the calculated value of formula (1) is preferably 5 to 45 in the following formula (4), and is preferably -5 to 5 in the following formula (5).
• C, Mn, Cr, Cu, Ni, Mo, W, Nb, N, and Ti represent the content of each element in mass% (the content is 0 (zero) percent for elements that are not contained) ⁇ 10 ⁇ formula 1 ⁇ 45 , ⁇ 0.25 ⁇ formula 2 ⁇ ⁇ 0.20 , and 0.10 ⁇ formula 3 ⁇ 0.20 ⁇ 10 ⁇ formula 1 ⁇ 5 , ⁇ 0.35 ⁇ formula 2 ⁇ ⁇ 0.25 , and 0.025 ⁇ formula 3 ⁇ 0.10 ⁇ 10 ⁇ formula 1 ⁇ ⁇ 5 , ⁇ 0.39 ⁇ formula 2 ⁇ ⁇ 0.35 , and ⁇ 0.15 ⁇ formula 3 ⁇ 0.025
• the composition contains the balance Fe and unavoidable impurities.
• the foregoing basic composition may further contain one or more selectable elements selected from Ti: 0.19% or less, Nb: 0.25% or less, W: 1.1% or less, and Co: 0.45% or less, as needed.
• Titanium and niobium form carbides, and can reduce the solid-solution carbon. This makes it possible to reduce hardness. Excessively high Ti and Nb contents may deteriorate toughness, and the Ti and Nb contents are limited to 0.19% or less for Ti, and 0.25% or less for Nb when containing these elements.
• Tungsten and cobalt are elements that improve the pitting corrosion resistance.
• excessively high W and Co contents may deteriorate toughness, and increase the material cost.
• the W and Co contents are limited to 1.1% or less for W, and 0.45% or less for Co when containing these elements.
• the present invention uses a steel pipe material of the composition described above.
• the method of production of the steel pipe material, or a seamless stainless steel pipe is not particularly limited, and any known seamless steel pipe production method may be used.
• a molten steel of the foregoing composition is made into steel using a steel making process such as by using a converter furnace, and formed into a steel pipe material, for example, a billet, using a method such as continuous casting, and ingot casting-slab rolling.
• the steel pipe material is heated, and hot worked using a known pipe manufacturing process, for example, such as the Mannesmann-plug mill process, and the Mannesmann-mandrel mill process to produce a seamless steel pipe of the foregoing composition.
• the process that follows the production of the steel pipe from the steel pipe material is not particularly limited.
• the steel pipe is subjected to quenching, in which the steel pipe is heated to a temperature equal to or greater than the Ac 3 transformation point, and air cooled to a cooling stop temperature of 100°C or less at a cooling rate of 0.1°C/s or more, and this is followed by tempering at a temperature equal to or less than the Ac 1 transformation point.
• the steel pipe is subjected to quenching, in which the steel pipe is reheated to a temperature equal to or greater than the Ac 3 transformation point, maintained for preferably at least 5 min, and air cooled to a cooling stop temperature of 100°C or less.
• the quenching heating temperature is less than the Ac 3 transformation point, heating cannot be made in the single austenite phase region, and a sufficient martensite structure cannot be obtained in the subsequent cooling. In this case, the desired high strength cannot be obtained. For this reason, the quenching heating temperature is limited to a temperature equal to or greater than the AC 3 transformation point.
• air cooling means a cooling rate of 0.1°C/s or more.
• the tempering is a process by which the steel pipe is heated to a temperature equal to or less than the Ac 1 transformation point, maintained for preferably at least 10 min, and air cooled.
• the tempering temperature is higher than the Ac 1 transformation point, the martensite phase precipitates after the tempering, and it is not possible to obtain the desired high toughness and excellent corrosion resistance. For this reason, the tempering temperature is limited to a temperature equal to or less than the Ac 1 transformation point.
• the Ac 3 transformation point (°C), and the Ac 1 transformation point (°C) can be measured by a Formaster test, in which the test piece is given a heating and cooling temperature history, and the transformation point is detected from a small displacement due to expansion and contraction.
• Molten steels of the compositions shown in Table 1 were made into steel with a converter furnace, and cast into billets (steel pipe material) by continuous casting. The steel pipe material was then hot worked with a model seamless rolling machine, and air cooled (cooling rate of 0.5°C/s) to produce a seamless steel pipe measuring 83.8 mm in outer diameter and 12.7 mm in wall thickness.
• the seamless steel pipe was cut to obtain a test material, which was then subjected to quenching and tempering under the conditions shown in Table 2.
• a test piece for structure observation was collected from the quenched and tempered test material, and was polished, and measured for residual austenite ( ⁇ ) amount by an X-ray diffraction method.
• ⁇ volume fraction 100 / 1 + I ⁇ R ⁇ / I ⁇ R ⁇
• Ia represents the integral intensity of ⁇
• R ⁇ represents a crystallographic theoretical value for ⁇
• I ⁇ represents the integral intensity of ⁇
• R ⁇ represents a crystallographic theoretical value for ⁇
• a strip specimen specified by API standard 5CT was collected from the quenched and tempered test material, and subjected to a tensile test according to the API specifications to determine its tensile characteristics (yield stress YS, tensile stress TS).
• the Ac 3 point (°C)and the Ac 1 point (°C) shown in Table 2 were measured by conducting a Formaster test for a test piece (measuring 4 mm in diameter ⁇ ⁇ 10 mm) collected from the quenched test material. Specifically, the test piece was heated to 500°C at 5°C/s, maintained for 10 minutes after raising the temperature to 920°C at 0.25°C/s, and cooled to room temperature at 2°C/s. The Ac 3 point (°C) and the Ac 1 point (°C) were found by detecting the expansion and contraction of the test piece with the temperature history.
• the SSC test was conducted according to NACE TM0177, Method A.
• the test environment was created by using a 0.165 mass% NaCl test solution after adjusting the solution pH to 3.5 by addition of 0.41 g/L of CH 3 COONa and HCl, and the test was conducted under a hydrogen sulfide partial pressure of 0.1 MPa, and an applied stress equal to 90% of the yield stress.
• the martensitic stainless steel seamless pipes of the present examples all had high strength with a yield stress of 758 MPa or more, and excellent SSC resistance that did not involve cracking even under the applied stress in the H 2 S environment. Comparative Examples outside the range of the present invention did not show excellent SSC resistance, though the desired levels of high strength were obtained.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Heat Treatment Of Articles (AREA)
• Heat Treatment Of Steel (AREA)

Applications Claiming Priority (2)

Publications (3)

Family

ID=62024768

Family Applications (1)

Country Status (7)

Cited By (1)

Families Citing this family (11)

Family Cites Families (12)

• 2017
  • 2017-09-13 EP EP17865353.1A patent/EP3533892B1/de active Active
  • 2017-09-13 US US16/343,829 patent/US20190241989A1/en not_active Abandoned
  • 2017-09-13 MX MX2019004721A patent/MX2019004721A/es unknown
  • 2017-09-13 WO PCT/JP2017/033008 patent/WO2018079111A1/ja active Application Filing
  • 2017-09-13 JP JP2017567270A patent/JP6315159B1/ja active Active
  • 2017-09-13 BR BR112019007842-8A patent/BR112019007842B1/pt active IP Right Grant
  • 2017-10-23 AR ARP170102946A patent/AR109869A1/es active IP Right Grant

Also Published As

Similar Documents

Legal Events