Low-temperature high-toughness petroleum drill rod and preparation method thereof

Abstract

The invention discloses a low-temperature high-toughness petroleum drill rod and a preparation method thereof, and belongs to the technical field of metallurgy. The petroleum drill rod comprises the following components in percentage by mass: 0.23%-0.28% of C, 0.17%-0.39% of Si, 0.9%-1.10% of Mn, less than or equal to 0.012% of P, less than or equal to 0.003% of S, 1.05%-1.15% of Cr, 1.05%-1.15% of Ni, 0.24%-0.32% of Mo, 0.03%-0.06% of Nb, 0.01%-0.03% of Ti, 0.003%-0.009% of Re, 0.009%-0.015% of Al, 0.009%-0.015% of Ca, less than or equal to 0.002% of O, less than or equal to 0.00015% of H, less than or equal to 0.003% of N and the balance of Fe and inevitable impurities. Through reasonable design of the components, the minimum yield strength of the pipe body respectively meets the requirements of 105ksi and 135ksi, that is, the room-temperature yield strength is respectively 724-931 MPa (G105L) and 931-1138 MPa (S135L), the tensile strength is respectively 793-1000 MPa (G105L) and 1000-1207 MPa (S135L), and the ductility is greater than or equal to 20%; the weld bearing capacity is higher than that of the pipe body; and the impact energy of the pipe body and the welding seam at-40 DEG C is greater than or equal to 100J and 60J. And the requirement for safe use of the high-strength drill rod of deep oil and gas development under complex extremely-low-temperature working conditions can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy and relates to a low-temperature high-toughness petroleum drill pipe and a preparation method thereof. Background Art

[0002] Some oil and gas fields located in cold areas have an ambient temperature as low as -40℃ in winter. Extreme low-temperature deep oil and gas production conditions place higher demands on the strength, low-temperature toughness, and safety and reliability of drill pipes. At present, the International Organization for Standardization (ISO), the American Petroleum Institute (API) and my country's national standard (GB / T29166--2021) only put forward requirements for the toughness of drill pipes at -20℃. Drill pipe manufacturers at home and abroad also mainly produce drill pipes that can meet the -20℃ low-temperature working environment. The relevant patents and technical literature also mainly involve drill pipes of various steel grades used in -20℃ low-temperature working environments. In addition, although there are also methods for preparing low-temperature drill pipes at -40℃ to -60℃ in the prior art, they only consider the control of inclusions and harmful elements in steelmaking raw materials, and the composition design and preparation process are not reasonable. It is urgent to develop high-toughness oil drill pipes for use in -40℃ working conditions. Summary of the invention

[0003] The purpose of the present invention is to solve the problems of unreasonable design and preparation process of low-temperature oil drill pipe components and poor low-temperature performance in the prior art, and to provide a low-temperature high-toughness oil drill pipe and a preparation method thereof. The strength, low-temperature toughness and safety reliability of the oil drill pipe manufactured by this method can meet the requirements of safe use in a low-temperature environment of about -40°C.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] In a first aspect, the present invention provides a low-temperature high-toughness oil drill pipe, wherein the steel composition of the oil drill pipe comprises, by mass percentage:

[0006] C: 0.23%~0.28%, Si: 0.17%~0.39%, Mn: 0.90%~1.10%, P≤0.012%, S≤0.003%, Cr: 1.05%~1.15% , Ni: 1.05% ~ 1.15%, Mo: 0.24% ~ 0.32%, Al: 0.009% ~ 0.015%, O ≤ 0.002%, H ≤ 0.00015%, N ≤ 0.003%.

[0007] A further improvement of the present invention is:

[0008] The steel grade composition also includes the following by mass percentage:

[0009] Nb: 0.03%~0.06%, Ti: 0.01%~0.03%, Re: 0.003%~0.009%, Ca: 0.009%~0.015%, Fe and impurities.

[0010] In a second aspect, the present invention provides a method for preparing the above-mentioned low-temperature high-toughness petroleum drill pipe, characterized in that it comprises the following steps in sequence:

[0011] Steelmaking, continuous casting, perforation, hot rolling, primary heat treatment, pipe end thickening, full pipe body quenching and tempering heat treatment, drill pipe friction welding, drill pipe heat treatment and secondary heat treatment of welding parts; the drill pipe includes a drill pipe body and a drill pipe joint;

[0012] The steelmaking process comprises the following steps in sequence: batching; steelmaking in an electric furnace or oxygen-blown converter, feeding rare earth wire, the mass percentage of which is 0.003% to 0.009%; refining outside the furnace and vacuum degassing, feeding calcium silicon wire, the mass percentage of which is 0.009% to 0.015%.

[0013] A further improvement of the present invention is:

[0014] The following steps are also included:

[0015] After secondary heat treatment of the welding parts of the oil drill pipe, it is subjected to non-destructive testing and internal coating treatment.

[0016] The continuous casting is:

[0017] The molten steel obtained from steelmaking is cast into rod-shaped continuous casting billets, and electromagnetic stirring and soft pressure reduction technology are used in the process.

[0018] The piercing and hot rolling are as follows:

[0019] The continuous casting billet obtained by continuous casting is heated in an annular heating furnace with a heating furnace temperature of 1180°C to 1230°C for 100 to 120 minutes, hot-pierced at a temperature of 1150°C to 1200°C, hot-rolled at a temperature of 960°C to 1170°C, and then sizing, straightening, cooling and sawing are performed in sequence.

[0020] The initial heat treatment is:

[0021] The invention adopts a heat treatment process of heating in a protective atmosphere furnace, quenching and high-temperature tempering; the heating temperature of the quenching is 890°C to 910°C, the holding time is 40 to 60 minutes, the internal and external water spray quenching, and the cooling rate is 20°C / s to 30°C / s; the temperature of the high-temperature tempering is 630°C to 680°C, and the tempering time is 90 to 120 minutes; water cooling after high-temperature tempering; and then sizing and hot straightening are carried out, the hot straightening temperature is 570°C to 600°C, and then water cooling is carried out.

[0022] The whole tube body quenching and tempering heat treatment is as follows:

[0023] A heat treatment process of controlled atmosphere furnace heating, quenching + high-temperature tempering is adopted; the heating temperature of the quenching is 880°C to 900°C, the holding time is 40 to 60 minutes, the internal and external water spray quenching, and the cooling rate is 20°C / s to 30°C / s; the temperature of the high-temperature tempering is controlled at 620°C to 680°C, and the tempering time is 90 to 120 minutes; water cooling is performed after high-temperature tempering.

[0024] The drill pipe friction welding and drill pipe heat treatment are as follows:

[0025] The inertia friction welding method is adopted; at the moment after the friction welding upsetting, PAG quenching liquid is sprayed on the outer surface of the welding area and compressed air is sprayed on the inner surface for quenching, and then medium-frequency induction heating is performed to 680℃~700℃ for tempering; finally, the flash and burrs inside and outside the welding area are processed.

[0026] The secondary heat treatment of the welding part is as follows:

[0027] The welding area is heated to a temperature of 860°C to 880°C by medium frequency induction heating, and PAG quenching liquid is sprayed on the outer surface of the welding area and compressed air is sprayed on the inner surface for quenching, and then medium frequency induction heating is used to heat the welding area to a temperature of 650°C to 700°C for tempering.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The invention discloses a low-temperature high-toughness petroleum drill pipe, wherein the chemical composition of the steel of the drill pipe is C: 0.23% to 0.28%, Mn: 0.90% to 1.10%, Cr: 1.05% to 1.15%, Ni: 1.05% to 1.15%, and Mo: 0.24% to 0.32% by mass percentage. Among them, C is a strengthening element in steel. Mn is mainly used to improve the hardenability of steel, thereby improving strength. Cr is mainly used to improve the hardenability of steel, thereby improving strength. Ni is mainly used to improve the hardenability of steel, thereby improving strength and low-temperature toughness. Mo is mainly used to improve the hardenability of steel to improve strength and tempering stability. Through the reasonable design of its components, the minimum yield strength of its pipe body reaches the requirements of 105ksi and 135ksi, that is, the room temperature yield strength is 724-931MPa (G105L) and 931-1138MPa (S135L), the tensile strength is 793-1000MPa (G105L) and 1000-1207MPa (S135L), and the elongation is ≥20%; the load-bearing capacity of the weld is higher than that of the pipe body; the Charpy impact toughness of the pipe body and weld at -40℃ is ≥100J and 60J. It can meet the needs of safe use of high-strength drill pipes in deep oil and gas development under complex extreme low temperature conditions.

[0030] Furthermore, the composition of the low-temperature high-toughness oil drill pipe also includes appropriate amounts of Nb, Ti, Re, Ca and Fe. Re has multiple functions of purifying molten steel, refining grains, modifying inclusions and alloying. Ca with a mass ratio of 0.24% to 0.32% can improve the properties and morphology of inclusions, thereby improving the toughness of steel. Nb with a mass ratio of 0.03% to 0.06% forms NbC and NbN with C and N added to steel, which has the effect of hindering the growth of austenite grains and refining grains, thereby improving strength and toughness. Ti with a mass ratio of 0.01% to 0.03% forms TiC and TiN with C and N added to steel, which has the effect of hindering the growth of austenite grains and refining grains, thereby improving strength and toughness.

[0031] The present invention also discloses a method for preparing a low-temperature high-toughness oil drill pipe. When steel is smelted, rare earth wire with a mass percentage of 0.003% to 0.009% is added, which has multiple functions of purifying molten steel, refining grains, modifying inclusions, and alloying. Silicon calcium (Si-Ca) wire with a mass percentage of 0.009% to 0.015% is added to improve the properties and morphology of inclusions, thereby improving the toughness of steel. In this method, the addition of rare earth elements can refine grains, purify impurities, and improve the low-temperature toughness of the oil drill pipe. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0033] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] The present invention is further described in detail below in conjunction with specific embodiments:

[0035] The present invention is described in detail below by taking the production of G105L and S135L low-temperature high-toughness oil drill pipes as an example.

[0036] Example 1

[0037] The steel composition of low temperature and high toughness oil drill pipe is as follows by mass percentage:

[0038] C: 0.23%, Si: 0.17%, Mn: 0.90%, P: 0.008%, S: 0.002%, Cr: 1.05%, Ni: 1.05%, Mo: 0.24%, Al: 0.009%, O: 0.001%, H: 0.00005%, N: 0.0015%, Nb: 0.03%, Ti: 0.01%, Re: 0.003%, Ca: 0.009%, Fe and impurities. The manufacturing method is carried out according to the following steps:

[0039] (1) Steelmaking

[0040] Ingredients, electric furnace steelmaking, sponge iron and high-quality scrap steel as raw materials, feeding rhenium (Re) wire, after refining outside the furnace and vacuum degassing, to obtain the above chemical composition, feeding silicon calcium (Si-Ca) wire to modify the inclusions in the steel.

[0041] (2) Continuous casting

[0042] The molten steel is cast into rod-shaped continuous casting billets. Electromagnetic stirring and soft pressure reduction technology are used during the continuous casting process to control the segregation in the continuous casting billets.

[0043] (3) Piercing and hot rolling

[0044] The continuous casting billet is heated in an annular heating furnace at a temperature of 1180°C for 100 minutes, hot pierced at 1150°C, hot rolled at 960°C, and then sized, straightened, cooled, sawed, and subjected to non-destructive testing.

[0045] (4) Initial heat treatment

[0046] The heat treatment process of protective atmosphere furnace heating (to prevent decarburization), quenching + high temperature tempering is adopted. The quenching heating temperature is controlled at 890℃, the holding time is 40 minutes, the internal and external water spray quenching, the cooling rate is 20℃ / s, to ensure that the martensite structure is basically obtained after quenching; the tempering temperature is controlled at 630℃ (S135L) and 660℃ (G105L), the tempering time is 90 minutes, in order to obtain fine and uniform tempered troostite, the grain size is 8-9, and water cooling is carried out after tempering to avoid possible temper brittleness; then sizing and hot straightening are carried out, the straightening temperature is controlled at 570℃, and then water cooling; after non-destructive inspection, sawing to the appropriate size.

[0047] (5) Thickening of pipe ends

[0048] The pipe end is heated to 1070°C, and upsetting is performed 3 to 5 times using the inner and outer diameter dies and the temperature gradient of the pipe end to obtain the inner and outer thickened size and shape of the pipe end.

[0049] (6) Full pipe body quenching and tempering heat treatment

[0050] The controlled atmosphere furnace is used for heating, the quenching heating temperature is controlled at 880℃, the holding time is 40 minutes, the internal and external water spray quenching, the cooling rate is 20℃ / s, to ensure that basically all the martensitic structures are obtained after quenching; the tempering temperature is controlled at 620℃ (S135L) and 660℃ (G105L), the tempering time is 90 minutes, in order to obtain fine and uniform tempered troostite, the grain size is 9 to 10, and water cooling is performed after tempering to avoid possible temper brittleness; then non-destructive and dimensional inspections are carried out.

[0051] (7) Friction welding and heat treatment of drill pipe body and drill pipe joint

[0052] The inertia friction welding method is used to reasonably control the rotation speed, back pressure and upsetting pressure so that the drill pipe body and the drill pipe joint are firmly welded together. At the moment after the friction welding upsetting (880℃~900℃), the PAG quenching liquid is sprayed on the outer surface of the welding area and the compressed air is sprayed on the inner surface for quenching, and then the medium frequency induction heating is heated to 680℃ for tempering. The weld structure is tempered troostite, and the heat affected zone is a mixed structure of tempered troostite, pearlite and ferrite. Then the flash and burrs inside and outside the welding area are processed. This heat treatment method organically combines phase change and deformation, which can significantly improve the comprehensive performance of the weld. Medium frequency induction heating and high temperature tempering are conducive to the removal of flash and burrs inside and outside the welding area.

[0053] (8) Secondary heat treatment of welding parts

[0054] The welding area is heated to 860℃ by medium frequency induction heating, and PAG quenching liquid is sprayed on the outer surface of the welding area and compressed air is sprayed on the inner surface for quenching. Then medium frequency induction heating is performed to 650℃ (S135L) and 680℃ (G105L), and the temperature is kept for 5 minutes for tempering. Then non-destructive testing is performed.

[0055] (9) Inner coating

[0056] Whether to apply internal coating depends on the usage scenario of low-temperature and high-toughness oil drill pipe.

[0057] Example 2

[0058] The steel composition of low temperature and high toughness oil drill pipe is as follows by mass percentage:

[0059] C: 0.28%, Si: 0.39%, Mn: 1.10%, P: 0.011%, S: 0.003%, Cr: 1.15%, Ni: 1.15%, Mo: 0.32%, Al: 0.015%, O: 0.0015%, H: 0.00015%, N: 0.0025%, Nb: 0.06%, Ti: 0.03%, Re: 0.009%, Ca: 0.015%, Fe and impurities. The manufacturing method thereof is carried out according to the following steps:

[0060] (1) Steelmaking

[0061] Ingredients, oxygen-blown converter steelmaking, feeding rhenium (Re) wire, blast furnace molten iron and high-quality scrap steel as raw materials, refining outside the furnace and vacuum degassing, to obtain the above chemical composition, feeding silicon calcium (Si-Ca) wire to modify the inclusions in the steel.

[0062] (2) Continuous casting

[0063] The molten steel is cast into rod-shaped continuous casting billets. Electromagnetic stirring and soft pressure reduction technology are used during the continuous casting process to control the segregation in the continuous casting billets.

[0064] (3) Piercing and hot rolling

[0065] The continuous casting billet is heated in an annular heating furnace at a temperature of 1230°C for 120 minutes, hot pierced at 1200°C, hot rolled at 1170°C, and then sized, straightened, cooled, sawed, and subjected to non-destructive testing.

[0066] (4) Initial heat treatment

[0067] The heat treatment process of protective atmosphere furnace heating (to prevent decarburization), quenching + high temperature tempering is adopted. The quenching heating temperature is controlled at 910℃, the holding time is 60 minutes, the internal and external water spray quenching, and the cooling rate is 30℃ / s to ensure that the martensite structure is basically obtained after quenching; the tempering temperature is controlled at 650℃ (S135L) and 680℃ (G105L), and the tempering time is 120 minutes to obtain fine and uniform tempered troostite, with a grain size of 8 to 9. After tempering, water cooling is carried out to avoid possible temper brittleness; then sizing and hot straightening are carried out, the straightening temperature is controlled at 600℃, and then water cooling is carried out; after non-destructive inspection, sawing is carried out to the appropriate size.

[0068] (5) Thickening of pipe ends

[0069] The pipe end is heated to 1120°C, and upsetting is performed five times using the inner and outer diameter dies and the temperature gradient of the pipe end to obtain the inner and outer thickened size and shape of the pipe end.

[0070] (6) Full pipe body quenching and tempering heat treatment

[0071] The controlled atmosphere furnace is used for heating, the quenching heating temperature is controlled at 900℃, the holding time is 60 minutes, the internal and external water spray quenching, the cooling rate is 30℃ / s, to ensure that basically all the martensitic structures are obtained after quenching; the tempering temperature is controlled at 640℃ (S135L) and 680℃ (G105L), the tempering time is 120 minutes, in order to obtain fine and uniform tempered troostite, the grain size is 9 to 10, and water cooling is performed after tempering to avoid possible temper brittleness; then non-destructive and dimensional inspections are carried out.

[0072] (7) Friction welding and heat treatment of drill pipe body and drill pipe joint

[0073] The inertia friction welding method is used to reasonably control the rotation speed, back pressure and upsetting pressure so that the drill pipe body and the drill pipe joint are firmly welded together. At the moment after the friction welding upsetting (880℃~900℃), PAG quenching liquid is sprayed on the outer surface of the welding area and compressed air is sprayed on the inner surface for quenching, and then medium frequency induction heating is heated to 700℃ for tempering. The weld structure is tempered troostite, and the heat affected zone is a mixed structure of tempered troostite, pearlite and ferrite. Then the flash and burrs inside and outside the welding area are processed. This heat treatment method organically combines phase change and deformation, which can significantly improve the comprehensive performance of the weld. Medium frequency induction heating and high temperature tempering are conducive to the removal of flash and burrs inside and outside the welding area.

[0074] (8) Secondary heat treatment of welding parts

[0075] The welding area is heated to 880℃ by medium frequency induction heating, and PAG quenching liquid is sprayed on the outer surface of the welding area and compressed air is sprayed on the inner surface for quenching. Then medium frequency induction heating is performed to 670℃ (S135L) and 700℃ (G105L), and the temperature is kept for 5 minutes for tempering. Then non-destructive testing is performed.

[0076] (9) Inner coating

[0077] Whether to apply internal coating depends on the usage scenario of low-temperature and high-toughness oil drill pipe.

[0078] Example 3

[0079] The steel composition of low temperature and high toughness oil drill pipe is as follows by mass percentage:

[0080] C: 0.25%, Si: 0.28%, Mn: 1.0%, P: 0.007%, S: 0.002%, Cr: 1.08%, Ni: 1.09%, Mo: 0.28%, Al: 0.013%, O: 0.0015%, H: 0.00007%, N: 0.0023%, Nb: 0.05%, Ti: 0.02%, Re: 0.006%, Ca: 0.0012%, Fe and impurities. The manufacturing method is carried out according to the following steps:

[0081] (1) Steelmaking

[0082] Ingredients, oxygen-blown converter steelmaking, blast furnace molten iron and high-quality scrap steel as raw materials, feeding rhenium (Re) wire, after refining outside the furnace and vacuum degassing, to obtain the above chemical composition, feeding silicon calcium (Si-Ca) wire to modify the inclusions in the steel.

[0083] (2) Continuous casting

[0084] The molten steel is cast into rod-shaped continuous casting billets. Electromagnetic stirring and soft pressure reduction technology are used during the continuous casting process to control the segregation in the continuous casting billets.

[0085] (3) Piercing and hot rolling

[0086] The continuous casting billet is heated in a ring heating furnace at a temperature of 1200°C for 110 minutes, hot pierced at 1175°C, hot rolled at 1060°C, and then sized, straightened, cooled, sawed, and subjected to non-destructive testing.

[0087] (4) Initial heat treatment

[0088] The heat treatment process of protective atmosphere furnace heating (to prevent decarburization), quenching + high temperature tempering is adopted. The quenching heating temperature is controlled at 900℃, the holding time is 50 minutes, the internal and external water spray quenching, the cooling rate is 25℃ / s, to ensure that the martensite structure is basically obtained after quenching; the tempering temperature is controlled at 650℃, the tempering time is 115 minutes, in order to obtain fine and uniform tempered troostite, the grain size is 8-9, and water cooling is carried out after tempering to avoid possible temper brittleness; then sizing and hot straightening are carried out, the straightening temperature is controlled at 585℃, and then water cooling; after non-destructive inspection, sawing is carried out to the appropriate size.

[0089] (5) Thickening of pipe ends

[0090] The pipe end is heated to 1100°C, and upsetting is performed 3 to 5 times using the inner and outer diameter dies and the temperature gradient of the pipe end to obtain the inner and outer thickened size and shape of the pipe end.

[0091] (6) Full pipe body quenching and tempering heat treatment

[0092] The controlled atmosphere furnace is used for heating, the quenching heating temperature is controlled at 890℃, the holding time is 50 minutes, the internal and external water spray quenching, the cooling rate is 25℃ / s, to ensure that basically all martensitic structures are obtained after quenching; the tempering temperature is controlled at 650℃, the tempering time is 105 minutes, in order to obtain fine and uniform tempered troostite, the grain size is 9 to 10, and water cooling is performed after tempering to avoid possible temper brittleness; then non-destructive and dimensional inspections are carried out.

[0093] (7) Friction welding and heat treatment of drill pipe body and drill pipe joint

[0094] The inertia friction welding method is used to reasonably control the rotation speed, back pressure and upsetting pressure so that the drill pipe body and the drill pipe joint are firmly welded together. At the moment after the friction welding upsetting (880℃~900℃), the PAG quenching liquid is sprayed on the outer surface of the welding area and the compressed air is sprayed on the inner surface for quenching, and then the medium frequency induction heating is heated to 690℃ for tempering. The weld structure is tempered troostite, and the heat affected zone is a mixed structure of tempered troostite, pearlite and ferrite. Then the flash and burrs inside and outside the welding area are processed. This heat treatment method organically combines phase change and deformation, which can significantly improve the comprehensive performance of the weld. Medium frequency induction heating and high temperature tempering are conducive to the removal of flash and burrs inside and outside the welding area.

[0095] (8) Secondary heat treatment of welding parts

[0096] The welding area is heated to 870℃ by medium frequency induction heating, and PAG quenching liquid is sprayed on the outer surface of the welding area and compressed air is sprayed on the inner surface for quenching, and then medium frequency induction heating is performed to 675℃, and the temperature is kept for 5 minutes for tempering. Then non-destructive testing is performed.

[0097] (9) Inner coating

[0098] Whether to apply internal coating depends on the usage scenario of low-temperature and high-toughness oil drill pipe.

[0099] According to the method for preparing low-temperature high-toughness petroleum drill pipe of the present invention, the low-temperature high-toughness petroleum drill pipe described in Table 1 can also be prepared, wherein O not listed is ≤0.002%, H is ≤0.00015%, N is ≤0.0025%, and the balance is Fe and unavoidable impurities:

[0100] Table 1

[0101]

[0102]

[0103] The working principle of the present invention is as follows:

[0104] In order to meet the comprehensive requirements of drill pipe strength, plasticity, low-temperature toughness, welding adaptability, etc., its chemical composition and preparation process must be reasonably designed.

[0105] In terms of composition design, the present invention intends to use medium and low C, add Mn, Cr, Ni, Mo, Nb, Ti micro-alloying, add Re element, control harmful elements such as P, S, O, H, N in steel, use Al and Si for full deoxidation, and perform Ca treatment on the molten steel. The functions and content ranges of the main elements are as follows:

[0106] C: It is a strengthening element in steel. However, too low carbon content is not conducive to improving the hardenability of steel and the strength of steel; too high carbon content is not conducive to the toughness of steel. It is advisable to control it within the range of 0.23% to 0.28%.

[0107] Si: It is a common element in steel and should be controlled within the range of 0.17% to 0.39%.

[0108] Mn: Mainly used to improve the hardenability of steel, thereby increasing strength. It is best to control it within the range of 0.90% to 1.10%.

[0109] Cr: Mainly used to improve the hardenability of steel, thereby increasing strength. It is best to control it within the range of 1.05% to 1.15%.

[0110] Ni: Mainly used to improve the hardenability of steel, thereby improving strength and low-temperature toughness. It is best to control it within the range of 1.05% to 1.15%.

[0111] Mo: Mainly used to improve the hardenability of steel to increase strength and tempering stability. It is best to control it within the range of 0.24% to 0.32%.

[0112] Nb: Added into steel to form NbC and NbN with C and N in steel, it has the function of hindering the growth of austenite grains and refining grains, thereby improving strength and toughness. It is best to control it within the range of 0.03% to 0.06%.

[0113] Ti: When added to steel, it forms TiC and TiN with C and N in the steel, which has the effect of hindering the growth of austenite grains and refining grains, thereby improving strength and toughness. It is best to control it within the range of 0.01% to 0.03%.

[0114] Re: It has multiple functions of purifying molten steel, refining grains, modifying inclusions, and alloying. It is best to control it within the range of 0.003% to 0.009%.

[0115] Ca: It can improve the properties and morphology of inclusions, thereby increasing the toughness of steel. It is best to control it within the range of 0.009% to 0.015%.

[0116] Al: It is an important deoxidizer. It forms oxides with oxygen to deoxidize, and forms nitrides with nitrogen to partially eliminate the adverse effects of N. It also refines grains and improves strength and toughness. It is best to control it within the range of 0.009% to 0.015%.

[0117] P: Harmful element, mainly affecting the plasticity and toughness of steel. It is advisable to control P ≤ 0.012%.

[0118] S: Harmful element, mainly affecting the plasticity, toughness and corrosion resistance of steel. It is advisable to control S ≤ 0.003%.

[0119] O: Harmful element, mainly affects the plasticity, toughness and corrosion resistance of steel. It is advisable to control O≤0.002%.

[0120] H: Harmful element, mainly affects the plasticity and toughness of steel. It is advisable to control H≤0.00015%.

[0121] N: Harmful element, mainly affects the plasticity and toughness of steel. It is advisable to control N≤0.0025%.

[0122] In summary, the composition of 105ksi and 135ksi steel grade low temperature and high toughness drill pipe is as follows by mass percentage: C: 0.23%~0.28%, Si: 0.17%~0.39%, Mn: 0.9%~1.10%, P≤0.012%, S≤0.003%, Cr: 1.05%~1.15%, Ni: 1.05%~1.15%, Mo: 0.24%~0.32%, Nb: 0.03%~0.06%, Ti: 0.01%~0.03%, Re: 0.003%~0.009%, Al: 0.009%~0.015%, Ca: 0.009%~0.015%, O≤0.002%, H≤0.00015%, N≤0.003%, and the balance is Fe and unavoidable impurities.

[0123] At the same time, Mo / P ≥ 20 is controlled to control the adverse effect of P segregation on toughness; Al / N ≥ 3 is controlled to eliminate the adverse effect of N on toughness; (Ca+Re) / S ≥ 4 is controlled to control the effect of inclusion modification treatment and improve the toughness of steel.

[0124] In terms of drill pipe preparation technology, drill pipe products are mainly prepared through pure static steel smelting, continuous casting, perforation, hot rolling, sizing, straightening, pipe end thickening, heat treatment, friction welding drill pipe joints, weld heat treatment, non-destructive testing, internal coating (if necessary), etc. Through reasonable process parameter design and control, the drill pipe can obtain a fine and uniform microstructure, thereby achieving a reasonable match of strength, plasticity, and low-temperature toughness. The heat treatment process and performance of G105L low-temperature high-toughness oil drill pipe and S135L low-temperature high-toughness drill pipe are described in Table 2:

[0125] Table 2

[0126]

[0127] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A low temperature and high toughness oil drill pipe, characterized in that: The steel grade composition of the oil drill pipe includes the following by mass percentage: C: 0.23%~0.28%, Si: 0.17%~0.39%, Mn: 0.90%~1.10%, P≤0.012%, S≤0.003%, Cr: 1.05%~1.15% , Ni: 1.05% ~ 1.15%, Mo: 0.24% ~ 0.32%, Al: 0.009% ~ 0.015%, O ≤ 0.002%, H ≤ 0.00015%, N ≤ 0.003%.

2. The low temperature and high toughness petroleum drill pipe according to claim 1, characterized in that: The steel grade composition also includes by mass percentage: Nb: 0.03%~0.06%, Ti: 0.01%~0.03%, Re: 0.003%~0.009%, Ca: 0.009%~0.015%, Fe and impurities.

3. A method for preparing the low-temperature high-toughness petroleum drill pipe according to claim 2, characterized in that: The following steps are included in sequence: Steelmaking, continuous casting, perforation, hot rolling, primary heat treatment, pipe end thickening, full pipe body quenching and tempering heat treatment, drill pipe friction welding, drill pipe heat treatment and secondary heat treatment of welding parts; the drill pipe includes a drill pipe body and a drill pipe joint; The steelmaking process comprises the following steps in sequence: batching; steelmaking in an electric furnace or oxygen-blown converter, feeding rare earth wire, the mass percentage of which is 0.003% to 0.009%; refining outside the furnace and vacuum degassing, feeding calcium silicon wire, the mass percentage of which is 0.009% to 0.015%.

4. The method for preparing a low-temperature high-toughness petroleum drill pipe according to claim 3, characterized in that: The following steps are also included: After secondary heat treatment of the welding parts of the oil drill pipe, it is subjected to non-destructive testing and internal coating treatment.

5. The method for preparing a low-temperature high-toughness petroleum drill pipe according to claim 3, characterized in that: The continuous casting is: The molten steel obtained from steelmaking is cast into rod-shaped continuous casting billets, and electromagnetic stirring and soft pressure reduction technology are used in the process.

6. The method for preparing a low-temperature high-toughness petroleum drill pipe according to claim 5, characterized in that: The piercing and hot rolling are as follows: The continuous casting billet obtained by continuous casting is heated in an annular heating furnace with a heating furnace temperature of 1180°C to 1230°C for 100 to 120 minutes, hot-pierced at a temperature of 1150°C to 1200°C, hot-rolled at a temperature of 960°C to 1170°C, and then sizing, straightening, cooling and sawing are performed in sequence.

7. The method for preparing a low-temperature high-toughness petroleum drill pipe according to claim 6, characterized in that: The initial heat treatment is: The invention adopts a heat treatment process of heating in a protective atmosphere furnace, quenching and high-temperature tempering; the heating temperature of the quenching is 890°C to 910°C, the holding time is 40 to 60 minutes, the internal and external water spray quenching, and the cooling rate is 20°C / s to 30°C / s; the temperature of the high-temperature tempering is 630°C to 680°C, and the tempering time is 90 to 120 minutes; water cooling after high-temperature tempering; and then sizing and hot straightening are carried out, the hot straightening temperature is 570°C to 600°C, and then water cooling is carried out.

8. The method for preparing a low-temperature high-toughness petroleum drill pipe according to claim 6, characterized in that: The whole tube body quenching and tempering heat treatment is as follows: A heat treatment process of controlled atmosphere furnace heating, quenching + high-temperature tempering is adopted; the heating temperature of the quenching is 880°C to 900°C, the holding time is 40 to 60 minutes, the internal and external water spray quenching, and the cooling rate is 20°C / s to 30°C / s; the temperature of the high-temperature tempering is controlled at 620°C to 680°C, and the tempering time is 90 to 120 minutes; water cooling is performed after high-temperature tempering.

9. The method for preparing a low-temperature high-toughness petroleum drill pipe according to claim 8, characterized in that: The drill pipe friction welding and drill pipe heat treatment are as follows: The inertia friction welding method is adopted; at the moment after the friction welding upsetting, PAG quenching liquid is sprayed on the outer surface of the welding area and compressed air is sprayed on the inner surface for quenching, and then medium-frequency induction heating is performed to 680℃~700℃ for tempering; finally, the flash and burrs inside and outside the welding area are processed.

10. The method for preparing a low-temperature high-toughness petroleum drill pipe according to claim 9, characterized in that: The secondary heat treatment of the welding part is as follows: The welding area is heated to a temperature of 860°C to 880°C by medium frequency induction heating, and PAG quenching liquid is sprayed on the outer surface of the welding area and compressed air is sprayed on the inner surface for quenching, and then medium frequency induction heating is used to heat the welding area to a temperature of 650°C to 700°C for tempering.

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