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  • C21D7/00—Modifying the physical properties of iron or steel by deformation
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  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
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  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
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  • 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
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  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
  • C21D8/1222—Hot rolling
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  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
  • C21D8/1261—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest following hot rolling
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  • 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
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  • 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
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  • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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  • 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
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  • 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
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  • 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
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  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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  • C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt
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  • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
• • 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
  • C21D2211/001—Austenite
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  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/008—Martensite

Definitions

• Sulphide stress cracking resistant steel tubular product made from said steel, process for manufacturing a tubular product and use thereof
• the present invention relates to low alloy steels with a high yield strength that present an improved sulphide stress cracking behaviour.
• the present invention also relates to tubular products, such as tubes or pipes, made from said steel, as well as a process for manufacturing such tubular products.
• the present invention concerns use of such tubular products for well drilling, and/or for production, extraction and/or transportation of oil and gas .
• H 2 S hydrogen sulphide
• SSC sulphide stress cracking
• Sulphide stress cracking resistance is thus of particular importance for oil companies since it is relevant to the safety of equipment.
• the application US2006016520 provides a steel for steel pipes which comprises, on the percent by mass basis, C: 0.2 to 0.7%, Si: 0.01 to 0.8%, Mn: 0.1 to 1.5%, S: 0.005% or less, P: 0.03% or less, Al: 0.0005 to 0.1%, Ti: 0.005 to 0.05%, Ca: 0.0004 to 0.005%, N: 0.007% or less, Cr: 0.1 to 1.5%, Mo: 0.2 to 1.0%, Nb: 0 to 0.1%, Zr: 0 to 0.1%, V: 0 to 0.5% and B: 0 to 0.005%, with the balance being Fe and impurities, in which non-metallic inclusions containing Ca, Al, Ti, N, O, and S are present, and in the said inclusions (Ca %)/(Al %) is 0.55 to 1.72, and (Ca %)/(Ti %) is 0.7 to
• U-el means uniform elongation (%)
• TS means tensile strength (MPa).
• This steel pipe having the above described chemical composition, can be obtained, for example, by being heated at temperatures from 700 to 790°C, then being forced-cooled down to a temperature of lower than or equal to l00°C with the cooling rate of greater than or equal to l00°C/min at the temperature from 700 to 500°C.
• the steels should also present improved sulphide stress cracking performance, as well as corrosion resistance.
• An object of the present invention is therefore a steel having a chemical composition consisting of, in weight%, relative to the total weight of said chemical composition,
• the balance of the chemical composition of said steel being constituted by Fe and one or more residual elements, including Cu; and the chemical composition of said steel satisfying the following formula (1) between C, Si, Mn, Cr, Mo, V, Nb and Cu, the contents of which are expressed in weight%,
• the steel of the invention presents an improved sulphide stress cracking resistance than steels of the prior art.
• the steel of the present invention presents a yield strength preferably greater than or equal to 862 MPa (125 ksi).
• the yield strength is determined by tensile tests as defined in standards ASTM A370-17 and ASTM E8/E8M-l3a.
• the steel of the present invention is particularly useful for the production of tubular products for hydrocarbon wells containing hydrogen sulphide (H 2 S).
• Another object of the present invention concerns a tubular product, and in particular a tube or a pipe, made from a steel as previously defined.
• the present invention also relates to a process for manufacturing a tubular product, and in particular a tube or a pipe, comprising:
• the tubular product thus obtained from the steel of the invention presents an improved sulphide stress cracking resistance. It can therefore be used in oil and gas production.
• the present invention also relates to the use of such a tubular product for well drilling, and/or for production, extraction, transportation of oil and gas .
• Figure 1 disclo ses a graph displaying coefficient a on the x- axis and coefficient b on the y-axis, both coefficients a and b being determined according to the formulae previously defined.
• This figure 1 shows that the steel of the present invention (o), wherein both coefficients a and b satisfy formula ( 1 ) defined previously, present a better sulphide stress cracking resistance than comparative steels (x) .
• the chemical composition of the steel according to the present invention contains 0.32 ⁇ C ⁇ 0.46 % by weight, relative to the total weight of said chemical composition .
• the chemical composition of the steel contains carbon (C) in a content ranging from 0.32 to 0.46% by weight, relative to the total weight of said chemical composition; it being understood that the lower limit (0.32% by weight) being included, while the upper one (0.46 % by weight) being excluded.
• the steel thus obtained is less resistant to stress cracking .
• High carbon content meaning a content higher than 0.32% by weight, relative to the total weight of the chemical composition, enables a higher tempering temperature, which leads to a lower dislocation density and thus po sitive effect on SSC resistance.
• the carbon content is greater than or equal to 0.46% by weight, quench cracks can occur as well as the formation of coarse precipitates that are detrimental to SSC resistance.
• the carbon content is preferably higher than or equal to 0.34% (0.34% ⁇ C) by weight, more preferentially higher than or equal to 0.41 % (0.41 % £ C) by weight, relative to the total weight of the chemical composition.
• the carbon content is preferably lower than or equal to 0.44% (C ⁇ 0.44% ) by weight, relative to the total weight of the chemical composition.
• the carbon content is higher than or equal to 0.34% by weight and lower than or equal to 0.44% by weight, relative to the total weight of the chemical composition .
• the chemical composition of the steel according to the present invention preferably contains 0.34 ⁇ C ⁇ 0.44% by weight, relative to the total weight of said chemical compo sition .
• the carbon content is higher than or equal to 0.41 % by weight and lower than or equal to 0.44% by weight, relative to the total weight of the chemical composition.
• the chemical composition of the steel according to the present invention more preferably contains 0.41 ⁇ C ⁇ 0.44% by weight, relative to the total weight of said chemical composition.
• the chemical composition of the steel according to the present invention further contains 0. 10 ⁇ Si ⁇ 0.45 % by weight, relative to the total weight of said chemical composition .
• the chemical composition of the steel contains silicon (Si) in a content ranging from 0. 10 to 0.45 % by weight, relative to the total weight of said chemical composition; it being understood that both lower (0. 10% by weight) and higher (0.45 % by weight) limits being included.
• a minimum content of 0. 10% by weight of silicon comes from steel de-oxidation. This element is also needed to retard softening phenomenon during high temperature tempering . Eventually, it helps to increase the strength after quenching and tempering .
• silicon makes the steel brittle.
• the silicon content is preferably higher than or equal to 0. 12% (0. 12% ⁇ Si) by weight, relative to the total weight of the chemical composition.
• the silicon content is preferably lower than 0.38 % (Si ⁇ 0.38 % ) by weight, relative to the total weight of the chemical composition.
• the silicon content is higher than or equal to 0. 12% by weight and lower than 0.38 % by weight, relative to the total weight of the chemical composition.
• the chemical composition of the steel according to the present invention preferably contains 0. 12 ⁇ Si ⁇ 0.38 % by weight, relative to the total weight of said chemical composition.
• the chemical composition of the steel according to the present invention further contains 0. 10 ⁇ Mn ⁇ 0.50 % by weight, relative to the total weight of said chemical composition.
• the chemical composition of the steel contains manganese (Mn) in a content ranging from 0. 10 to 0.50 % by weight, relative to the total weight of said chemical composition; it being understood that both lower (0. 10% by weight) and higher (0.50% by weight) limits being included.
• Manganese is required to avoid free sulfur (S ) in the steel by the formation of MnS .
• This element is beneficial to hot workability as well as hardenability due to solute solution strengthening, thus indirectly also to SSC by enabling a more homogeneous through thickness tempered martensite microstructure.
• Mn segregates at steel mid thickness and affects negatively SSC resistance.
• the manganese content is preferably higher than or equal to 0.20% (0.20 % ⁇ Mn) by weight, relative to the total weight of the chemical composition.
• the manganese content is preferably lower than or equal to 0.40% (Mn ⁇ 0.40 %) by weight, relative to the total weight of the chemical composition.
• the manganese content preferably ranges from 0.20 to 0.40% by weight, relative to the total weight of the chemical compo sition .
• the chemical composition of the steel according to the present invention preferably contains 0.20 ⁇ Mn ⁇ 0.40% by weight, relative to the total weight of said chemical composition.
• the chemical composition of the steel according to the present invention further contains 0.30 ⁇ Cr ⁇ 1 .25 % by weight, relative to the total weight of said chemical composition .
• the chemical composition of the steel contains chromium (Cr) in a content ranging from 0.30 to 1 .25 % by weight, relative to the total weight of said chemical composition; it being understood that both lower (0.30% by weight) and higher ( 1 .25 % by weight) limits being included.
• the steel thus obtained is less resistant to corrosion .
• Cr improves the SSC resistance by limiting the corrosion rate and thus the hydrogen production rate.
• This beneficial role of Cr is attributed to the formation of a thin layer of enriched Cr oxide, identified as mainly CrOOH, between base material and iron sulphide scales.
• the chromium content is preferably higher than or equal to 0.70% (0.70% ⁇ Cr) by weight, relative to the total weight of the chemical composition.
• the chromium content is preferably lower than or equal to 1.20 % (Cr ⁇ 1 .20% ) by weight, and more preferentially lower than or equal to 1 . 10% (Cr ⁇ 1. 10 % ) by weight, relative to the total weight of the chemical compo sition.
• the chromium content preferably ranges from 0.30 to 1 .20% by weight, and more preferentially from 0.30 to 1 . 10% by weight, relative to the total weight of the chemical composition.
• the chemical composition of the steel according to the present invention preferably contains 0.30 ⁇ Cr ⁇ 1 .20% by weight, and more preferentially 0.30 ⁇ Cr ⁇ 1 . 10% by weight, relative to the total weight of said chemical composition.
• the chemical composition of the steel according to the present invention further contains 1 . 10 ⁇ Mo ⁇ 2. 10 % by weight, relative to the total weight of said chemical composition .
• the chemical composition of the steel contains molybdenum (Mo) in a content ranging from 1.10 to 2.10% by weight, relative to the total weight of said chemical composition; it being understood that the lower limit (1.10% by weight) being excluded, while the upper one (2.10% by weight) being included.
• Mo is beneficial to hardenability.
• the presence of molybdenum also makes it possible to increase the tempering temperature, without changing other process parameters, improving thus SSC resistance.
• the molybdenum content is preferably higher than or equal to 1.15% (1.15% ⁇ Mo) by weight, relative to the total weight of the chemical composition.
• the molybdenum content is preferably lower than or equal to 1.60% (Mo ⁇ 1.60%) by weight, and more preferentially lower than or equal to 1.51% (Mo ⁇ 1.51%) by weight, and even more preferentially lower than or equal to 1.40% (Mo ⁇ 1.40%) relative to the total weight of the chemical composition.
• the molybdenum content is preferably higher than 1.10% by weight and lower than or equal to 1.60% by weight, and more preferentially this content ranges from 1.15 to 1.60% by weight, and even more preferentially from 1.15 to 1.51% by weight relative to the total weight of the steel.
• the chemical composition of the steel according to the present invention preferably contains 1.10 ⁇ Mo ⁇ 1.60, and more preferentially 1.15 ⁇ Mo ⁇ 1.60% by weight, and even more preferentially 1.15 ⁇ Mo ⁇ 1.51% by weight relative to the total weight of said chemical composition.
• the chemical composition of the steel according to the present invention further contains 0.10 ⁇ V ⁇ 0.30% by weight, relative to the total weight of said chemical composition.
• the chemical composition of the steel contains vanadium (V) in a content ranging from 0.10 to 0.30% by weight, relative to the total weight of said chemical composition; it being understood that both lower (0.10% by weight) and higher (0.30% by weight) limits being included.
• vanadium forms fine carbides that have a positive impact on SSC resistance.
• a saturation effect occurs when vanadium represents more than 0.30% by weight of the total weight of the steel.
• the vanadium content is preferably higher than or equal to 0.11% (0.11% ⁇ V) by weight, and more preferentially higher than or equal to 0.125% (0.125% ⁇ V) by weight, relative to the total weight of the chemical composition.
• the vanadium content is preferably lower than or equal to
• V ⁇ 0.25% by weight, and more preferentially lower than or equal to 0.21% (V ⁇ 0.21%) by weight, relative to the total weight of the chemical composition.
• the vanadium content preferably ranges from 0.11 to 0.25% by weight, and more preferentially from 0.125 to 0.25% by weight, and even more preferentially from 0.125 to 0.21% by weight, relative to the total weight of the chemical composition.
• the chemical composition of the steel according to the present invention preferably contains 0.11 ⁇ V ⁇ 0.25%, more preferentially 0.125 ⁇ V ⁇ 0.25% by weight, and even more preferentially 0.125 ⁇ V ⁇ 0.21% by weight, relative to the total weight of said chemical composition.
• the chemical composition of the steel according to the present invention further contains 0.01 ⁇ Nb ⁇ 0.10% by weight, relative to the total weight of said chemical composition.
• the chemical composition of the steel contains niobium (Nb) in a content ranging from 0.01 to 0.10% by weight, relative to the total weight of said chemical composition; it being understood that both lower (0.01% by weight) and higher (0.10% by weight) limits being included.
• the maximum niobium content is limited to 0. 10% by weight of the total weight of the steel to avoid that coarse primary NbC carbides form. Indeed, these precipitates are deleterious to SSC resistance .
• niobium are needed to limit prior austenitic grain size.
• the niobium content is preferably higher than or equal to 0.022% (0.022% ⁇ Nb) by weight, relative to the total weight of the chemical composition.
• the niobium content is preferably lower than or equal to 0.05 % (Nb ⁇ 0.05 % ) by weight, and more preferentially lower than or equal to 0.045 % (Nb ⁇ 0.045 % ) by weight relative to the total weight of the chemical composition.
• the niobium content preferably ranges from 0.01 to 0.05 % by weight, and more preferentially from 0.022 to 0.045 % by weight, relative to the total weight of the chemical composition .
• the chemical composition of the steel according to the present invention preferably contains 0.01 ⁇ Nb ⁇ 0.05 % by weight, and more preferentially 0.022 ⁇ Nb ⁇ 0.045 % by weight, relative to the total weight of said chemical composition.
• residual elements refers to inevitable elements resulting from the steel production and casting processes .
• the sum of residual element contents is preferably lower than 0.4% by weight of the total weight of the chemical composition.
• the balance of the chemical composition of the steel according to the present invention is made of Fe and residual elements resulting from the steel production and casting processes, including Cu, and also anyone of As, P, S , N, Ni, Al, Co, Sn, B , Ti, W and mixtures thereof.
• the amount of Cu is lower than or equal to 0. 10% in weight.
• the amount of As is lower than or equal to 0.05 % in weight.
• the amount of P is lower than or equal to 0.03 % in weight.
• the amount of S is lower than or equal to 0.01 % in weight.
• the amount of N is lower than or equal to 0.01 % in weight.
• the amount of Ni when present as a residual element, alone or in combination with one or more other elements in the chemical composition of the steel according to the invention, is lower than or equal to 0. 10% in weight.
• the amount of Al is lower than or equal to 0. 10% in weight.
• the amount of Co is lower than or equal to 0. 10% in weight.
• the amount of Sn is lower than or equal to 0.03 % in weight.
• the amount of B is lower than or equal to 0.003 % in weight.
• the amount of Ti when present as a residual element, alone or in combination with one or more other elements in the chemical composition of the steel according to the invention, is lower than or equal to 0. 10% in weight.
• the amount of W is lower than or equal to 0.05 % in weight.
• the chemical composition of the steel according to the present invention contains one or more residual elements including Cu, P, S , N, Ni, Al, Co, Sn, B, Ti, W and mixtures therefore, the amounts of said elements, expressed in weight% , relative to the total weight of said chemical composition, are as follows : Cu ⁇ 0. 1 0
• the chemical composition of the steel according to the present invention may further contain W preferably ⁇ 0.05 % by weight, and more preferably ⁇ 0.04% by weight, relative to the total weight of said chemical composition.
• the chemical composition of the steel may further contain tungsten (W) preferably in a content lower than or equal to 0.05 % by weight, and more preferably lower than or equal to 0.04% by weight, relative to the total weight of said chemical composition.
• M 6 C carbides where the metal (M) is tungsten (W) , trigger deleterious effects on SSC resistance.
• the content of tungsten has therefore to remain preferably lower than or equal to 0.05 % by weight, and more preferably lower than or equal to 0.04% by weight, relative to the total weight of said chemical composition.
• the chemical composition of the steel according to the present invention may further contain preferably Cu ⁇ 0. 10% by weight, relative to the total weight of said chemical composition.
• the chemical composition of the steel may further contain copper (Cu) preferably in a content lower than or equal to 0. 10 % by weight, relative to the total weight of said chemical composition. Above 0. 10% by weight, copper may lead to undesirable increase of hardness for a given level of yield strength.
• B , Ti and Al may be added on purpose, meaning that these elements may be added or not in a deliberate way, but in any case limited below specific amounts .
• the chemical composition of the steel according to the present invention preferably contains B ⁇ 0.003 % , and more preferentially B ⁇ 0.0025 % by weight, relative to the total weight of said chemical composition.
• the chemical composition of the steel according to the present invention may further contain titanium (Ti) .
• the chemical composition may further contain Ti, even when said chemical composition is free from boron (B) .
• Ti is also contained in a content preferably lower than or equal to 0. 10% by weight, and more preferably lower than or equal to 0.04% by weight, relative to the total weight of said chemical compo sition .
• Ti is added on purpose and its content is limited, i.e. preferably lower than or equal to 0. 10 % by weight, relative to the total weight of said chemical composition.
• Ti may be useful when it comes to grain growth during elaboration, since such grain growth is deleterious to SSC resistance .
• content of titanium is higher than 0. 10% by weight of the total weight of the chemical compo sition of the steel, coarse nitrides precipitates form that are then deleterious to SSC resistance.
• the chemical composition of the steel according to the present invention may further contain aluminium (Al) as this element is used for de-oxidation during the melting process.
• Al aluminium
• its contents is preferably lower than or equal to 0. 10 % by weight, relative to the total weight of said chemical composition.
• the chemical composition of the steel according to the present invention preferably contains Al ⁇ 0. 10% by weight, relative to the total weight of said chemical composition. Above 0. 10% by weight, aluminium forms inclusions that may be detrimental to SSC resistance.
• the content of nitrogen (N) is preferably lower than or equal to 0.01 % by weight, relative to the total weight of the chemical composition. N forms coarse carbo-nitrides that are deleterious to SSC resistance. Other elements such as Ca and REM (rare earth metals) can also be present as unavoidable residual elements . P and S decrease grain cohesion and are therefore detrimental to toughness.
• the microstructure of the steel according to the present invention is preferably made of at least 90 % of tempered martensite, more preferentially more than 95 % of tempered martensite, and better still more than 99% of tempered martensite .
• a tempered martensite is obtained after final cooling of the steel.
• a tempered martensite is a martensite that has undergone a tempering treatment as defined in the process according to the invention.
• the quenched and tempered tubular product obtained by the process of the invention is made of steel presenting a tempered martensitic micro structure, meaning that the microstructure of this steel is preferably made of at least 90 % , more preferentially more than 95 % , and better still more than 99% of tempered martensite.
• the steel according to the present invention has a microstructure made of tempered martensite with a prior austenite grain size of less than or equal to 22.4p m that is greater than or equal to 8 in Standard ASTM E l 12- 13 format.
• the prior austenite grain size corresponds to the grain size of the austenite from which martensite is formed.
• the present invention also relates to a tubular product, and in particular a tube or a pipe, made from a steel as previously defined.
• tubular product is a seamless tube or a seamless pipe .
• Another object of the present invention concerns a process for manufacturing a tubular product as previously defined.
• tubular product made from steel according to the present invention is obtained according to conventional hot forming methods known by the man skilled in the art.
• the steel according to the present invention may be melted by commonly-used melting practices and commonly-used casting process such as the continuous casting or the ingot casting blooming methods .
• the steel is then heated to a temperature ranging from 1 100 °C and l 300°C, so that at all points the temperature reached is favorable to the high rates of deformation the steel will undergo during hot forming .
• the maximum temperature is lower than l 300°C to avoid burning .
• the hot ductility of the steel is negatively impacted.
• the semi finished product is then hot formed between 900°C and l 300°C in at least one step .
• a tubular product having the desired dimensions is thus obtained.
• the tubular product is then austenitized, i.e . heated up to an austenitization temperature (AT) where the microstructure is austenitic. This temperature should be within the austenitic range.
• AT austenitization temperature
• the austenitization temperature ranges from Ac3 (°C) to l 000 °C; if AT is less than Ac3 , the microstructure will not be fully austenitic and we may not reach the minimum of 90% martensitic steel after quench. Above l 000 °C, the austenite grains grow undesirably large and lead to a coarser final structure, which impacts negatively toughness and SSC resistance .
• the tubular product made of steel according to the present invention is then kept at the austenitization temperature AT for an austenitization time At of at least 2 minutes, the obj ective being that at all points of the tube, the temperature reached is at least equal to the austenitization temperature.
• the temperature should be homogeneous throughout the tube .
• the austenitization time At shall not be above 60 minutes because above such duration, the austenite grains grow undesirably large and lead to a coarser final structure. This would be detrimental to toughness and SSC resistance.
• the austenitized tubular product made of steel according to the present invention is then cooled to the ambient temperature. This cooling may either be performed in water (water quench) or in oil (oil quench) . In this manner, a quenched tubular product made of steel is obtained which preferably comprises in percentage of at least 90% of martensite, more preferentially at least 95 % of martensite, and better still at least 99% of martensite.
• the quenched tubular product made of steel according to the present invention is then tempered, i.e. heated up at a tempering temperature (TT) ranging from 500°C to Ac l (°C) , and preferably ranging from 600°C to Ac l (°C) . Tempering must be done below Ac l to avoid any phase transformation.
• TT tempering temperature
• Such tempering step is done during a tempering time Tt between 5 and 120 minutes .
• the tempering time is between 10 and 60 min. This leads to a quenched and tempered steel tubular product.
• the quenched and tempered steel tubular product according to the invention is then cooled down to the ambient temperature using either water or air cooling .
• the tubular product thus obtained may further undergo additional finishing steps, such as sizing or straightening .
• sequence (e) is repeated at least one more time.
• sequence (e) is performed successively at least two times during the process of the present invention.
• the process of the present invention comprises :
• sequences (e) and (f) of the process are repeated at least one more time .
• sequences (e) and (f) are performed at least two times during the process of the present invention.
• the process of the present invention comprises :
• the quenched and tempered steel tubular product is then useful for well drilling, and/or for production, extraction, transportation of oil and gas.
• the present invention also concerns use of a tubular product as previously defined for well drilling, and/or for production, extraction, transportation of oil and gas .
• compositions of steels according to the present invention (A-E) and comparative steels (F-P) have been prepared from the elements indicated in the table 1 below, the amounts of which are expressed as percent by weight, relative to the total weight of the chemical composition . Underlined values in the following table 1 are not in conformance with the invention. Table 1: tested steels
• the steels (A-P) having the chemical compositions described in the table 1 above have been heated and then hot formed into seamless steel pipes of the desired dimensions by hot working using the Mannesmann-plug mill process.
• the microstructure, mechanical behavior and SSC resistance of the seamless steel pipes (A-P) thus obtained are summarized in the following table 4.
• the SSC resistance of the seamless steel pipes (A-K and N) is also shown in figure 1.
• - PAG is the prior austenite grain size index as defined in standard ASTM El 12-13.
• - YS in MPa and ksi is the yield strength obtained in tensile test as defined in standards ASTM A370- 17 and ASTM E8/E8M- l 3a.
• SSC is the sulphide stress corrosion cracking resistance evaluated according standard NACE TM0 177 -2016 Method A.
• the SSC test consists in immersing the test specimens under load in an aqueous solution adjusted to pH 3.5 with the addition of acetic acid and sodium acetate in a test solution of 5 mass% NaCl.
• the solution temperature is 24°C
• H 2 S is at 0. 1 atm.
• C02 is at 0.9 atm.
• the testing duration is
• the inventors were flabbergasted to observe that comparative steel F having elemental contents within the composition ranges of the invention but having a chemical composition that does not satisfy formula ( 1 ) , also exhibit lower yield strength and worse sulphide stress cracking resistance than steels according to the present invention (A-E) .

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• 2019
  • 2019-04-29 US US17/043,910 patent/US20210032730A1/en not_active Abandoned
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