EP3450585A1 - Ölbohrlochrohr für expandierbares rohr - Google Patents

Ölbohrlochrohr für expandierbares rohr Download PDF

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Publication number
EP3450585A1
EP3450585A1 EP16915083.6A EP16915083A EP3450585A1 EP 3450585 A1 EP3450585 A1 EP 3450585A1 EP 16915083 A EP16915083 A EP 16915083A EP 3450585 A1 EP3450585 A1 EP 3450585A1
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EP
European Patent Office
Prior art keywords
pipe
less
oil well
content
phase
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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EP16915083.6A
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English (en)
French (fr)
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EP3450585A4 (de
Inventor
Kensuke Nagai
Manabu Wada
Noboru Hasegawa
Hirohito IMAMURA
Masakazu Ozaki
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Nippon Steel Corp
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Nippon Steel and Sumitomo Metal Corp
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Publication of EP3450585A1 publication Critical patent/EP3450585A1/de
Publication of EP3450585A4 publication Critical patent/EP3450585A4/de
Withdrawn legal-status Critical Current

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    • 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
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • 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
    • 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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing 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
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/44—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
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • 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
    • C21D2211/002—Bainite
    • 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
    • C21D2211/005—Ferrite
    • 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
    • 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
    • C21D2211/009—Pearlite

Definitions

  • the present invention relates to an oil well pipe for expandable tubular.
  • Expandable tubular is a technique (construction method) of expanding a steel pipe, which is inserted in an oil well or gas well, in the oil well or gas well.
  • the steel pipe used in this technique is called "oil well pipe for expandable tubular”.
  • Patent Document 1 discloses an oil well pipe for expandable tubular having a specific chemical composition and having a ferrite fraction of a metallographic microstructure of a base metal of from 50 to 95%.
  • Patent Document 2 discloses an oil well pipe for expandable tubular having a specific chemical composition, wherein the microstructure is a two-phase structure composed of a martensite-austenite constituent having an area ratio of from 2 to 10% and a soft phase, and the soft phase is composed of one or more of ferrite, high-temperature tempered martensite, and high-temperature tempered bainite.
  • Patent Document 3 discloses an oil well pipe for expandable tubular manufactured by quenching and tempering an electric resistance welded steel pipe having a specific chemical composition.
  • Patent Document 4 discloses an oil well pipe for expandable tubular manufactured by quenching and tempering a seamless steel pipe having a specific chemical composition.
  • Patent Documents 1 and 2 disclose an oil well pipe for expandable tubular including a DP steel (Dual Phase steel; for example, a steel containing a soft ferrite phase and a hard martensite phase).
  • DP steel Dual Phase steel; for example, a steel containing a soft ferrite phase and a hard martensite phase).
  • Patent Document 3 discloses an oil well pipe for expandable tubular whose metallographic microstructure is composed of tempered martensite as an oil well pipe for expandable tubular having excellent toughness after expansion.
  • Patent Document 3 an oil well pipe for expandable tubular described in Patent Document 3 may be demanded to further improve flawless pipe expandability and flawed pipe expandability.
  • Patent Document 4 discloses an oil well pipe for expandable tubular having a chemical composition with a small content of Al and manufactured by quenching and tempering a steel pipe.
  • An object of one aspect of the invention is to provide an oil well pipe for expandable tubular which achieves both flawless pipe expandability and flawed pipe expandability.
  • Means for solving the problem described above includes the following aspects.
  • an oil well pipe for expandable tubular which achieves both flawless pipe expandability and flawed pipe expandability.
  • a numerical range expressed by "x to y" includes the values of x and y in the range as the minimum and maximum values, respectively.
  • % indicating the content of a component (element) means “% by mass”.
  • content of C carbon
  • C content the content of C (carbon)
  • the content of other elements may also be referred to similarly.
  • oil well pipe includes both steel pipes used for oil wells and steel pipes used for gas wells.
  • martensite not modified means martensite not tempered
  • bainite means bainite not tempered
  • the oil well pipe for expandable tubular (hereinafter, also referred to as “oil well pipe according to the disclosure”) is an oil well pipe for expandable tubular, containing, in terms of % by mass: 0.020 to 0.080% of C, 0.50% or less of Si, 0.30 to 1.60% of Mn, 0.030% or less of P, 0.010% or less of S, 0.005 to 0.050% of Ti, and 0.010 to 0.500% of Al, and the balance being Fe and impurities, wherein, in a metallographic microstructure, an area fraction (hereinafter, also referred to as "first phase fraction") of a first phase composed of ferrite is from 90.0% to 98.0% and an area fraction (hereinafter, also referred to as "second phase fraction") of a second phase composed of one or more selected from the group consisting of tempered martensite, tempered bainite, and pearlite is from 2.0% to 10.0%.
  • first phase fraction an area fraction of a first phase composed of ferrite
  • area fraction of the first phase including ferrite means an area fraction (%) of the first phase with respect to the entire metallographic microstructure in a metallographic micrograph showing the metallographic microstructure of an oil well pipe.
  • area fraction a second phase composed of one or more selected from the group consisting of tempered martensite, tempered bainite, and pearlite means an area fraction (%) of the second phase with respect to the entire metallographic microstructure in a metallographic micrograph showing the metallographic microstructure of an oil well pipe.
  • the sum of the area fraction (%) of the first phase and the area fraction of the second phase is 100%.
  • both flawless pipe expandability i.e., properties of being able to be expanded in a state in which there is no flaw on the outer surface
  • flawed pipe expandability i.e., properties of being able to be expanded in a state in which there is a flaw on the outer surface
  • the oil well pipe of the disclosure has a chemical composition, containing, in terms of % by mass, 0.020 to 0.080% of C, 0.50% or less of Si, 0.30 to 1.60% of Mn, 0.030% or less of P, 0.010% or less of S, 0.005 to 0.050% of Ti, and 0.010 to 0.500% of Al, and the balance being Fe and impurities.
  • the above chemical composition contributes to both improvement of flawless pipe expandability and improvement of flawed pipe expandability.
  • the area fraction of the first phase composed of ferrite is from 90.0% to 98.0%
  • the area fraction of the second phase composed of one or more selected from the group consisting of tempered martensite, tempered bainite, and pearlite is from 2.0% to 10.0%.
  • the first phase fraction of 90.0% or more and the second phase fraction of 10.0% or less contribute to improvement of flawed pipe expandability.
  • the reason for this is considered to be that the occurrence of voids (cracks) initiating from flaws on the outer surface, propagation of the voids, and coalescence of the voids are suppressed by the first phase fraction is 90.0% or more, and the second phase fraction is 10.0% or less (i.e., by a structure mainly composed of soft ferrite).
  • the fact that the second phase is composed of one or more selected from the group consisting of tempered martensite, tempered bainite, and pearlite contributes to both improvement of flawed pipe expandability and improvement of flawed pipe expandability.
  • the second phase is composed of one or more selected from the above group, whereby the flawed pipe expandability is improved as compared with cases in which the second phase is composed of one or more selected from the group consisting of martensite and bainite (i.e., DP steel) (see, for example, Comparative Example 17).
  • the second phase is one or more selected from the group consisting of martensite and bainite
  • the difference in hardness between the soft first phase and the hard second phase is too large, strain concentration tends to occur in the metallographic microstructure, due to this strain concentration, generation of voids and coalescence of voids are likely to occur, and as a result, the flawed pipe expandability is considered to deteriorate.
  • the second phase composed of one or more selected from the group consisting of tempered martensite, tempered bainite, and pearlite in the disclosure is not too hard. Therefore, in the oil well pipe of the disclosure, occurrence of strain concentration, generation of voids, and coalescence of voids are suppressed, and as a result, flawed pipe expandability is considered to be improved.
  • the second phase composed of one or more selected from the group consisting of tempered martensite, tempered bainite, and pearlite in the disclosure can be distinguished from the second phase composed of one or more selected from the group consisting of martensite and bainite in a DP steel by observation with a metallographic micrograph.
  • the second phase in the disclosure is also distinguishable from the second phase in a DP steel also in that the phase contains a carbide (i.e., cementite; the same applies hereinafter).
  • a carbide i.e., cementite; the same applies hereinafter.
  • tempered martensite is distinguishable from martensite in that tempered martensite contains granular carbide.
  • tempered bainite is distinguishable from bainite in that tempered bainite contains granular carbide.
  • Pearlite of course, contains a carbide.
  • the second phase in the disclosure also has an effect of improving the work hardening property of an oil well pipe to some extent. Therefore, the second phase is considered to contribute to flawless pipe expandability.
  • the first phase fraction of 98.0% or less and the second phase fraction of 2.0% or more contribute to improvement of flawless pipe expandability.
  • the reason for this is considered to be that the work hardening property is secured because the first phase fraction is 98.0% or less and the second phase fraction is 2.0% or more.
  • the oil well pipe of the disclosure is an electric resistance welded steel pipe.
  • the oil well pipe of the disclosure is an electric resistance welded steel pipe
  • variations in wall thickness i.e., eccentricity
  • the flawless pipe expandability and flawed pipe expandability are more excellent.
  • C is an element that improves flawless pipe expandability by improving the work hardening property of steel.
  • the C content is 0.020 to 0.080%.
  • the C content is preferably 0.030% or more.
  • the C content is preferably 0.070% or less.
  • Si is an element that functions as a deoxidizer for steel.
  • the flawless pipe expandability may deteriorate.
  • the oil well pipe of the disclosure is an electric resistance welded steel pipe, there is a possibility that an inclusion may be generated in the electric resistance welded portion.
  • the content of Si is 0.50% or less.
  • the Si content is preferably 0.03% or more, and more preferably 0.05% or more.
  • the content of Si is preferably less than 0.50%, and more preferably 0.45% or less from the viewpoint of further improving flawless pipe expandability.
  • Mn is an element having an effect of improving hardenability of steel. Mn is an element effective for rendering S harmless. Accordingly, Mn is an element that improves both flawless pipe expandability and flawed pipe expandability.
  • the Mn content is 0.30% or more.
  • the Mn content is preferably 0.33% or more.
  • the Mn content is preferably 1.50% or less.
  • P is an element that may exist as impurities in the steel.
  • the P content is 0.030% or less.
  • the P content may be 0%. From the viewpoint of further reducing the cost for dephosphorization, the P content may be 0.001% or more.
  • S is an element that can exist as an impurity in a steel.
  • the S content is 0.010% or less.
  • the S content may be 0%. From the viewpoint of further reducing the cost for desulfurization, the S content may be 0.001% or more.
  • Ti is an element that forms a carbonitride and contributes to crystal grain size refining.
  • the content of Ti is 0.005% or more.
  • the Ti content is preferably 0.010% or more.
  • the Ti content exceeds 0.050%, coarse TiN is generated, which leads to deterioration of flawed pipe expandability. Therefore, the Ti content is 0.050% or less.
  • the Ti content is preferably 0.045% or less.
  • Al is an element that functions as a deoxidizer for steel.
  • Al is also an element having a function of promoting ferrite formation.
  • Al Since Al has such functions, Al is an element that improves flawless pipe expandability and flawed pipe expandability.
  • the Al content is 0.010% or more.
  • the Al content exceeds 0.500%, the flawless pipe expandability deteriorates due to the decrease in the second phase fraction and the flawed pipe expandability also deteriorates due to the formation of an Al based inclusion. Therefore, the Al content is 0.500% or less.
  • the Al content is preferably 0.490% or less.
  • the Al content is more preferably 0.060% to 0.500%, further preferably 0.100% to 0.500%, and particularly preferably more than 0.100% to 0.500%.
  • the metallographic microstructure according to the disclosure i.e., a metallographic microstructure having a first phase fraction of from 90.0% to 98.0% and a second phase fraction of from 2.0% to 10.0% is more easily formed.
  • the area fraction of the first phase composed of ferrite is 90.0% or more.
  • the balance excluded from the above-described elements is Fe and impurities.
  • the impurity means a component contained in a raw material or a component mixed in a manufacturing process and not intentionally contained in a steel.
  • the impurities include O (oxygen), N (nitrogen), Sb, Sn, W, Co, As, Mg, Pb, Bi, H (hydrogen), and REM.
  • REM refers to a rare earth element, i.e., at least one element selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
  • O is preferably controlled to have a content of 0.006% or less.
  • N is preferably controlled to have a content of 0.010% or less.
  • Sb, Sn, W, Co, or As may be included in a content of 0.1% or less
  • Mg, Pb or Bi may be included in a content of 0.005% or less
  • H may be included in a content of 0.0004% or less, and the contents of the other elements need not particularly be controlled as long as being in a usual range.
  • the oil well pipe of the disclosure may contain one or more of: 0.100% or less of Nb, 1.00% or less of Ni, 1.00% or less of Cu, 0.50% or less of Mo, 1.00% or less of Cr, 0.100% or less of V, or 0.0060% or less of Ca.
  • these elements may be mixed as impurities. Therefore, the lower limit of the content of these elements is not particularly limited, and may be 0%.
  • Nb is an element contributing to improvement of strength and toughness.
  • the Nb content is preferably 0.100% or less.
  • the Nb content may be 0%, or may be more than 0%.
  • the Nb content is preferably 0.001 % or more, more preferably 0.005% or more, and particularly preferably 0.010% or more.
  • Ni is an element contributing to improvement of strength and toughness.
  • the Ni content is preferably 1.00% or less.
  • the Ni content may be 0%, or may be more than 0%.
  • the Ni content is preferably 0.01 % or more, and more preferably 0.05% or more.
  • Cu is an element effective for improving the strength of a base metal.
  • the Cu content is preferably 1.00% or less.
  • the Cu content may be 0%, or may be more than 0%.
  • the Cu content is preferably 0.01% or more, and more preferably 0.05% or more.
  • Mo is an element effective for improving the hardenability of steel and obtaining high strength.
  • the Mo content is preferably 0.50% or less.
  • the Mo content may be 0%, or may be more than 0%.
  • the Mo content is preferably 0.01% or more, and more preferably 0.05% or more.
  • Cr is an element for improving hardenability.
  • the Cr content is preferably 1.00% or less.
  • the Cr content may be 0%, or may be more than 0%.
  • the Cr content is preferably 0.01% or more, and more preferably 0.05% or more.
  • V is an element having effects similar to those of Nb.
  • the V content is preferably 0.100% or less.
  • the V content may be 0%, or may be more than 0%.
  • the V content is preferably 0.005% or more, and more preferably 0.010% or more.
  • Ca is an element that controls the form of a sulfide inclusion and improves low temperature toughness.
  • the Ca content is preferably 0.0060% or less.
  • the Ca content may be 0%, or may be more than 0%.
  • the Ca content is preferably 0.0005% or more, and more preferably 0.0010% or more.
  • the oil well pipe of the disclosure preferably satisfies the following Formula (1) from the viewpoint of electric resistance weldability: Mn / Si > 2.0 wherein, in Formula (1), Mn and Si each represent % by mass of each element.
  • Mn/Si is not particularly limited, and Mn/Si is preferably 40.0 or less.
  • the first phase fraction i.e., the first phase fraction (i.e., the area fraction of the first phase composed of ferrite) is from 90.0% to 98.0%.
  • the first phase fraction is preferably 91.0% or more.
  • the first phase fraction is preferably 97.0% or less.
  • the area fraction of the second phase fraction i.e., the area fraction of one or more selected from the group consisting of tempered martensite, tempered bainite, and pearlite
  • the area fraction of the second phase fraction is from 2.0% to 10.0%.
  • the second phase fraction is preferably 3.0% or more.
  • the second phase fraction is preferably 9.0% or less.
  • the outer diameter of the oil well pipe of the disclosure is preferably from 150 mm to 300 mm, and more preferably from 200 mm to 300 mm.
  • the wall thickness of the oil well pipe of the disclosure is preferably from 5.00 mm to 20.00 mm, and more preferably from 7.00 mm to 17.00 mm.
  • any method can be used as long as the method can produce an oil well pipe having the above-described chemical composition and metallographic microstructure, and there is no particular limitation.
  • the oil well pipe of the disclosure can be produced, for example, by quenching an as-rolled steel pipe (preferably an electric resistance welded steel pipe) having the above-described chemical composition, followed by tempering.
  • an as-rolled steel pipe preferably an electric resistance welded steel pipe having the above-described chemical composition
  • quenching means a process including a heating process in which a steel pipe is heated to an austenite region and a cooling process in which a steel pipe is cooled from an austenite region in this order, the cooling process including a step of rapid cooling (for example, secondary cooling described below).
  • quenching in the disclosure does not mean a process of forming a structure consisting only of martensite.
  • as-rolled steel pipe means a steel pipe which has not yet been heat treated after pipe-making.
  • An as-rolled steel pipe (preferably an electric resistance welded steel pipe) can be prepared by a known method.
  • the electric resistance welded steel pipe can be prepared by bending a hot-rolled steel sheet having the above-described chemical composition into a pipe shape to form an open pipe and welding an abutting portion of the obtained open pipe.
  • Production Method A includes quenching and then tempering an as-rolled steel pipe (preferably an electric resistance welded steel pipe) having the chemical composition described above.
  • an as-rolled steel pipe preferably an electric resistance welded steel pipe
  • quenching includes a heating process and a cooling process in this order.
  • the heating temperature in the heating process of quenching (hereinafter, also referred to as “quenching heating temperature T 1 ”) is preferably a temperature within the range of from 900°C to 1,100°C.
  • the heating time in the heating process of quenching is preferably from 180 s (seconds) to 3,600 s (seconds), and more preferably 300 s to 1,800 s.
  • the cooling process of quenching preferably includes:
  • the above-described metallographic microstructure i.e., a metallographic microstructure having a first phase fraction of from 90.0% to 98.0% and a second phase fraction of from 2.0% to 10.0%
  • a metallographic microstructure having a first phase fraction of from 90.0% to 98.0% and a second phase fraction of from 2.0% to 10.0% can be more easily formed.
  • the chemical composition of the oil well pipe is a chemical composition having a small content of Al which is an element promoting ferrite formation (for example, in the case of a chemical composition having an Al content of 0.100% or less), it is preferable to apply a cooling process including primary cooling and secondary cooling.
  • a metallographic microstructure having a first phase fraction of from 90.0% to 98.0% and a second phase fraction of from 2.0% to 10.0% is easy to form when a cooling process including primary cooling and secondary cooling is applied is presumed as follows.
  • a steel pipe after the heating process is cooled (i.e., slowly cooled) at a cooling rate of 10°C/s or less to the primary cooling stop temperature T 2 where the difference (T 1 - T 2 ) from the quenching heating temperature T 1 is from 20°C to 230°C.
  • the difference (T 1 - T 2 ) between the quenching heating temperature T 1 and the primary cooling stop temperature T 2 is 20°C or more and the cooling rate is 10°C/s or less, it is considered that the time during which the temperature of the steel pipe passes through the temperature range where ferrite is formed (hereinafter, also referred to as "ferrite forming zone passing time") can be increased to some extent. This promotes the formation of ferrite, and therefore it is considered that the first phase fraction of 90.0% or more and the second phase fraction of 10.0% or less are finally easily achieved.
  • the primary-cooled electric resistance welded steel pipe is cooled (i.e., "rapidly cooled") at a cooling rate of 30°C/s or more.
  • the cooling start temperature of the secondary cooling coincides with the cooling stop temperature T 2 of the primary cooling.
  • the secondary cooling stop temperature is a temperature of from 300°C to room temperature.
  • the metallographic microstructure of the disclosure in which the area fraction of a first phase composed of ferrite is from 90.0% to 98.0% and the area fraction of a second phase composed of one or more selected from the group consisting of tempered martensite, tempered bainite, and pearlite is from 2.0% to 10.0% can be easily formed.
  • Tempering in Production Method A includes a heating process and a cooling process in this order.
  • tempering heating temperature in the heating process of tempering is, for example, from 200°C to 670°C.
  • the heating time in the heating process of tempering is preferably from 180 s (seconds) to 1,800 s (seconds), and more preferably from 300 s to 900 s.
  • quenching was carried out as follows.
  • the pipe was primary cooled (slowly cooled) at the cooling rate of the primary cooling shown in Tables 3 and 4 until a temperature of the pipe reached the primary cooling stop temperature T 2 (i.e., secondary cooling start temperature) shown in Tables 3 and 4.
  • T 2 i.e., secondary cooling start temperature
  • Tempering was carried out by heating the electric resistance welded steel pipe which was secondary cooled to room temperature at a heating temperature (i.e., a tempering heating temperature) shown in Tables 3 and 4 for 600 s and then cooling the pipe to room temperature with water.
  • a heating temperature i.e., a tempering heating temperature
  • An oil well pipe of Comparative Example 17 was obtained in the same manner as in Example 1 except that the chemical composition was changed from Steel 1 to Steel 83 and the tempering was not carried out.
  • first phase fraction and second phase fraction were measured at a position to which the distance from the outer surface of the oil well pipe was 1/4 of the wall thickness (hereinafter, also referred to as "wall thickness 1/4 position") in a cross-section (specifically, a cross-section parallel to the pipe axis direction) at a position deviating at 90° in the circumferential direction of the pipe from the electric resistance welded portion of the oil well pipe.
  • the cross-section was polished, and then was etched with Nital reagent.
  • a metallographic micrograph of the wall thickness 1/4 position in the etched cross-section was taken by a scanning electron microscope (SEM) at a magnification of 1,000 times for 10 fields of view (as an actual area of the cross section of 0.15 mm 2 ).
  • the area fraction of a first phase composed of ferrite and the area fraction of a second phase composed of one or more selected from the group consisting of tempered martensite, tempered bainite, and pearlite were obtained, respectively.
  • Image processing was carried out using a small general purpose image analyzer LUZEX AP manufactured by NIRECO CORPORATION.
  • Tables 5 and 6 also show the type of the second phase (second phase type).
  • a sample pipe having a length of 3,000 mm cut out from each oil well pipe was expanded at a pipe expansion ratio of 25% using a pipe expanding plug.
  • pipe expansion with a pipe expansion ratio of 25% means expanding the pipe until a circumferential length of the outer surface was increased by 25%.
  • the notched sample was expanded at a pipe expansion ratio of 16.5% using a pipe expanding plug.
  • the oil well pipes of Examples 1 to 70 having the chemical composition of the disclosure wherein the first phase fraction was from 90.0% to 98.0%, the second phase fraction was from 2.0% to 10.0%, and the second phase type was one or more selected from the group consisting of tempered martensite, tempered bainite, and pearlite achieved both flawless pipe expandability and flawed pipe expandability.
  • Fig. 1 is a scanning electron micrograph (SEM micrograph; magnification: 1,000 times) showing the metallographic microstructure of the oil well pipe of Example 1.
  • the micrographing position of the SEM micrograph in Fig. 1 is the same as the micrographing position of the SEM micrograph in the measurement of the first phase fraction and the second phase fraction (i.e., a position deviating at 90° in the circumferential direction of the pipe from the electric resistance welded portion, and the position to which the distance from the outer surface is 1/4 of the wall thickness) (this also applies to Fig. 2 , Fig. 3A, and Fig. 3B to be described below).
  • the SEM micrograph of Fig. 1 was micrographed after polishing a cross-section of the oil well pipe and then etched with a Nital reagent (this also applies to Fig. 2 , Fig. 3A, and Fig. 3B to be described below).
  • the first phase composed of ferrite can be confirmed as a smooth region surrounded by grains, and the second phase composed of tempered bainite and tempered martensite can be confirmed as the other region.
  • a carbide i.e., cementite
  • cementite can be confirmed as a white dot.
  • Fig. 2 is an SEM micrograph (magnification: 1,000 times) showing the metallographic microstructure of the oil well pipe of Comparative Example 17 (DP steel).
  • the first phase composed of ferrite can be confirmed, and the second phase composed of martensite, which looks relatively white and featherlike as the other region, can be confirmed.
  • a carbide i.e., cementite
  • Fig. 3A is an SEM micrograph (magnification: 1,000 times) showing the metallographic microstructure of the oil well pipe of Comparative Example 14, and Fig. 3B is an SEM micrograph (magnification: 3,000 times) in which a part of Fig. 3A is enlarged.
  • a carbide i.e., cementite
  • a white dot As a result, it can be seen that the second phase was tempered martensite.

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EP16915083.6A 2016-08-30 2016-08-30 Ölbohrlochrohr für expandierbares rohr Withdrawn EP3450585A4 (de)

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CN109072370A (zh) 2018-12-21
US20190292637A1 (en) 2019-09-26

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