A high-toughness hydrogen sulfide corrosion-resistant drill pipe adopting a seamless steel pipe steel and a production method thereof, a seamless steel pipe, a heat treatment process and application

Abstract

The application provides a high-toughness anti-hydrogen sulfide corrosion drill steel pipe seamless steel pipe heat treatment process and application, and a production method thereof, and the composition is as follows: Cr: 1.00-1.30%, Ni: 0.50-0.70%, Mo: 0.90-1.10%, Al: 0.020-0.050%, V: 0.10-0.20%, Nb: 0.10-0.20%, C: 0.20-0.25%, Si: 0.15-0.30%, Mn: 0.50-0.70%, P: less than or equal to 0.010%, S: less than or equal to 0.0015%, and the balance is Fe and inevitable impurities. The application adopts Cr-Mo-Ni system and is supplemented with Nb, V and other micro-alloy elements to improve the strength and toughness and improve the SSC resistance. And through twice quenching and tempering treatment, the dislocation density of the material is reduced, and the loading strength of the NACE TM0177 standard A solution is passed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of alloy steel, and particularly relates to a high-strength and high-toughness anti-H2S corrosion drill pipe seamless steel pipe steel and a production method, a seamless steel pipe and a heat treatment process and application thereof, and is suitable for 10,000-meter deep well oilfield exploitation. BACKGROUND

[0002] In recent years, with the increasing consumption of oil energy, the exploration and development of oil and gas fields are facing the challenges of deep burial, high temperature, high pressure, and rich H2S gas in complex and harsh working conditions. When oil well pipes and other special oil pipes are used in deep and ultra-deep wells containing H2S and other corrosive media, various corrosion failure phenomena may occur, leading to oil and gas production reduction, and even causing oil well safety accidents. Therefore, oil well pipes are required to have higher strength and toughness, and at the same time have certain corrosion resistance. At present, 125 ksi is the highest level of anti-sulfur oil well pipe in API standard, and the highest level of 125 ksi anti-sulfur oil well pipe cannot meet the use requirements, and the development of 135 ksi anti-sulfur oil well pipe is imperative. With the increase of strength, the sensitivity of the material to H2S increases, and the development of oil well pipes with high strength and toughness and high SSC resistance is of great significance to the oil and gas exploration industry.

[0003] At present, many studies are trying to develop 135 ksi steel grade anti-sulfur oil well pipe, but the developed 135 ksi steel grade anti-sulfur oil well pipe is difficult to consider H2S corrosion while meeting the strength and toughness requirements, especially difficult to pass the NACE TM0177 standard A solution test. Moreover, the process flow of some oil well pipes in the research is long, and the production efficiency is low, so it is necessary to consider the chemical composition and process from the chemical composition and process, and develop oil well pipes with excellent anti-H2S corrosion performance and good strength and toughness, and a preparation method thereof, to ensure the safe and reliable use of oil well pipes in deep wells containing sulfur.

[0004] A Chinese patent with publication number CN117821861A published on April 5, 2024 discloses a 125 steel grade anti-sulfur pipe and a preparation method thereof. In the technical solution disclosed in the patent, the main principle is low carbon supplemented with Cr-Mo-Ni-V-Cu alloy addition, but in this technical solution, the addition of Ni and other noble metal elements is relatively high, reaching Ni: 1.0-2.0%, and the material cost is high.

[0005] A Chinese patent with publication number CN107177797A published on September 19, 2017 discloses a 130KSI, 135KSI grade corrosion-resistant drill pipe steel for oil and gas fields and a manufacturing method thereof. The main principle of the disclosed technical solution is to add Mn, Cr, Mo and other elements to improve the hardenability and strength-toughness of the steel, and to add trace amounts of V, Nb, Ni, Cu and other elements for strengthening, so as to obtain a tempered sorbite structure after one quenching and tempering treatment. However, the low-temperature Charpy impact energy at-20 DEG C is only greater than 42J, which cannot meet the impact toughness requirement of the drill pipe at a depth of 10,000 meters.

[0006] Therefore, it is necessary to provide a seamless steel pipe for a 10,000-meter deep well and capable of achieving a 135ksi steel grade high-strength anti-SSC drill pipe. SUMMARY

[0007] The present application aims to provide a high-strength-toughness anti-hydrogen sulfide corrosion drill pipe seamless steel pipe and a production method thereof. Cr-Mo-Ni is used and supplemented with Nb, V and other micro-alloy elements to improve the strength and toughness, and further improve the anti-SSC performance. By reducing the content of C and Mn, and increasing the content of Ni, Nb and other alloy elements, the low-temperature impact toughness of the material at-20 DEG C is improved.

[0008] The present application also aims to provide a seamless steel pipe and a heat treatment process. The seamless steel pipe is produced by using the above high-strength-toughness anti-hydrogen sulfide corrosion drill pipe seamless steel pipe, and through two quenching and tempering treatments, the dislocation density of the material is reduced, and the loading strength of the NACE TM0177 standard A solution is high.

[0009] The present application also aims to provide an application of the seamless steel pipe for 10,000-meter deep well oil field exploitation.

[0010] The specific technical solutions of the present application are as follows:

[0011] A high-strength-toughness anti-hydrogen sulfide corrosion drill pipe seamless steel pipe, comprising the following components by mass percentage:

[0012] Cr: 1.00-1.30%, Ni: 0.50-0.70%, Mo: 0.90-1.10%, Al: 0.020-0.050%, V: 0.10-0.20%, Nb: 0.10-0.20%, C: 0.20-0.25%, Si: 0.15-0.30%, Mn: 0.50-0.70%, P≤0.010%, S≤0.0015%, and the balance being Fe and unavoidable impurities.

[0013] The components of the high-strength-toughness anti-hydrogen sulfide corrosion drill pipe seamless steel pipe also satisfy:

[0014] T.O+[N]≤120ppm;

[0015] Preferably, the composition of the seamless steel pipe for the high-toughness anti-hydrogen sulfide corrosion drill also satisfies that the five harmful elements Sn, Sb, As, Pb and Bi are controlled to be ≤0.010%;

[0016] The composition of the seamless steel pipe for the high-toughness anti-hydrogen sulfide corrosion drill also satisfies: 0.8≤Ca / S≤2.0; Ca / S=[T.Ca-(0.31+0.02×T.Ca)×(0.99×T.O-5.44)] / (1.25×T.S).

[0017] The composition of the seamless steel pipe for the high-toughness anti-hydrogen sulfide corrosion drill also satisfies: T=-2×%Si+1.0×%Mn+1.3×%Mo+2.5×%Ni+2.0×(%V+%Nb)≥3.20%.

[0018] The above element symbols represent the mass percentage content of the element.

[0019] The composition of the seamless steel pipe for the high-toughness anti-hydrogen sulfide corrosion drill also satisfies:

[0020] R=-5×(%Si+%Mn)+12×%Mo+10×%Cr+20×%Nb+18×%V≥23.00%.

[0021] The above element symbols represent the mass percentage content of the element.

[0022] The application provides a production method of a high-toughness anti-hydrogen sulfide corrosion drill adopting a seamless steel pipe, which comprises the following technological process:

[0023] Electric arc furnace smelting→LF furnace refining→RH vacuum degassing→continuous casting→rolling.

[0024] The electric arc furnace smelting: the furnace charge of the electric furnace adopts low-sulfur scrap steel and pig iron, deoxidization and alloying are carried out during tapping, and the slag discharge amount is strictly controlled, the smelting end point S≤0.030%, and P≤0.120%.

[0025] The LF furnace refining: the elements C, Si, Mn, Cr, Ni, Mo, V and Nb are adjusted to target values, the white slag retention time is ≥20 min, and the smelting cycle is ≤70 min.

[0026] The RH vacuum degassing: the pure degassing time is ≥25 min, the soft blowing time is ≥20 min, and after vacuum treatment

[0027] [H]≤1.0ppm.

[0028] The present application is an effective means for modifying the sulfide morphology in the modified casting blank, and the calcium treatment not only modifies the original Al2O3 inclusions in the casting blank into liquid calcium aluminate inclusions, but also reduces the precipitation temperature of MnS inclusions and the amount of MnS inclusions precipitated by Ca preferentially combining with S during the cooling process. The Ca / S range is 0.8-2.0, and the effective calcium-sulfur ratio Ca / S formula is defined as follows:

[0029] Ca / S = [T.Ca-(0.31+0.02×T.Ca)×(0.99×T.O-5.44)] / (1.25×T.S). The Ca treatment formula is designed for this type of steel, and since the precipitated long strip sulfides will deteriorate the comprehensive performance of the material, the formula is obtained by thermodynamic calculation and fitting of the inclusions in the casting blank during the cooling process of the steel by related thermodynamic calculation software.

[0030] Wherein T.S is the total sulfur mass fraction in the steel, 10 -6 , i.e. the S content in the steel composition; T.Ca is the total calcium mass fraction in the steel, 10 -6 ; T.O is the total oxygen mass fraction in the steel, 10 -6 .

[0031] The continuous casting: round billet continuous casting, the tundish superheat is controlled to be 20-50℃ above the liquidus, and the continuous casting blank diameter D and the drawing speed v should meet D = 1029-1980×v-1470×v 2 , wherein the unit of the continuous casting blank diameter D is mm, and the unit of the drawing speed v is m / min. The relationship between the production continuous casting blank diameter and the drawing speed is designed to ensure the quality of the casting blank. In actual production, the diameter D specifications of the round billet are generally limited to 380mm, 450mm, 500mm, 600mm and 700mm.

[0032] Rolling: the casting blank is sent into a walking beam furnace, and the round steel heating temperature is ≥1230℃. The continuous casting blank diameter D and the heating time t should meet D = 180+0.42t, the unit of the continuous casting blank diameter D is mm, and the unit of the heating time t is min. The rolling temperature is ≥1180℃, the final rolling temperature is 700-950℃, and the rolling is followed by heat preservation or entering a slow cooling pit for slow cooling. The above rolling and finishing are used to form the material.

[0033] During calculation, the values before the units are directly substituted into the formula for calculation.

[0034] Preferably, the Φ380mm-Φ700mm continuous casting round billet is rolled into Φ90mm-Φ250mm round steel.

[0035] The application provides a heat treatment process of a seamless steel pipe, which adopts the high-strength and high-toughness hydrogen sulfide corrosion-resistant steel pipe to produce the seamless steel pipe.

[0036] The quenching is performed at a heating temperature W1 of AC3+30-50 DEG C, and the holding time t1 is determined by the wall thickness S of the steel pipe, t1=3.2*S, and water cooling is performed after the holding.

[0037] Wherein, the heating temperature W1 is in DEG C, the holding time t1 is in min, and the wall thickness S of the steel pipe is in mm;

[0038] The first tempering is performed at a first tempering temperature W2 of 650-720 DEG C, and the holding time t2 is determined by the wall thickness S of the steel pipe, t2=6*S, and air cooling is performed to room temperature after the holding.

[0039] Wherein, the first tempering temperature W2 is in DEG C, the holding time t2 is in min, and the wall thickness S of the steel pipe is in mm;

[0040] The second tempering is performed at a second tempering temperature W3 of W2-10 DEG C, and the holding time t3 is determined by the wall thickness S of the steel pipe, t3=5*S, and air cooling is performed after the holding.

[0041] Wherein, the second tempering temperature W3 is in DEG C, the holding time t3 is in min, and the wall thickness S of the steel pipe is in mm.

[0042] In the above formula, the values before the units are directly brought into the formula for calculation.

[0043] Some micro-alloying elements Mo, Nb, V and the like are added in the application, which are expected to be uniformly precipitated in the quenching process, so as to increase the strength, refine the grains, increase the number of irreversible hydrogen traps and improve the sulfur resistance, and the two times of quenching can further improve the uneven performance of the structure, reduce the stress concentration in the structure and effectively improve the comprehensive mechanical properties of the material.

[0044] A seamless steel pipe is obtained by the heat treatment process, the grain size at the 1 / 2 wall thickness of the end cross section of the seamless steel pipe is less than or equal to 20 microns, and the structure is tempered sorbite.

[0045] The non-metallic inclusion level of the seamless steel pipe is that the non-metallic A, B, C and D inclusions in the steel are all less than or equal to 1.0 level, and the total of the A, B, C and D is less than or equal to 2.5 level.

[0046] Preferably, the non-metallic inclusion level of the seamless steel pipe after heat treatment is: A class coarse system 0 level, A class fine system 0 level, B class coarse system ≤0.5 level, B class fine system ≤0.5 level, C class coarse system 0 level, C class fine system 0 level, D class fine system ≤0.5 level, D class coarse system ≤1.0 level; the total of A class, B class, C class and D class inclusion is ≤2.5 level.

[0047] The room temperature mechanical property of the seamless steel pipe is: tensile strength ≥1050MPa, yield strength ≥940MPa,

[0048] -20℃ impact energy ≥110J, elongation ≥16%, dislocation density is 3.0×10 13 / m -2 ~4.5×10 13 / m -2 ; low angle grain boundary ≥35%.

[0049] The seamless steel pipe passes the hydrogen sulfide corrosion resistance test for 720h without fracture under the conditions of loading strength of 80%SMYS, H2S partial pressure of 0.1MPa and temperature of 25℃ according to the standard A method of the American standard NACE TM0177.

[0050] The application of the seamless steel pipe provided by the application is obtained by the above method and is used for oil field exploitation in ten-thousand-meter deep well.

[0051] The main design idea of the application is as follows:

[0052] C: ensure the strength of the steel, improve the hardenability to increase the percentage of martensite transformation; in addition, increasing the C content can increase the number of carbonides precipitated during tempering, and these carbonides are good H traps; but too high C content not only causes its own segregation, but also greatly increases the segregation of Mn and P, thereby reducing the anti-SSC performance, so the C content is controlled at 0.20-0.25%.

[0053] Mn: improve the strength and hardenability of the steel, but Mn is an easy segregation element, and too much Mn is easy to segregate with S and P at the grain boundary, so it is not conducive to the anti-SSC performance; for the high Cr and Mo content designed in the application, the hardenability and strength of the steel are sufficient, so the Mn content is controlled at 0.50-0.70%.

[0054] Cr: improve the strength and hardenability, and improve the corrosion resistance, but too high Cr content will precipitate large size Cr 23 C6 carbonides at the grain boundary during tempering, which is not conducive to the H2S stress corrosion resistance, so the Cr content is controlled at 1.00-1.30%.

[0055] Mo: is an important solid solution strengthening and tempering precipitation strengthening element, but also to improve the hardenability of steel. Mo carbide in high temperature tempering precipitates to improve the tempering resistance, so to ensure high strength and high tempering temperature must be added enough Mo. In addition, Mo can also reduce the diffusion coefficient of P to reduce P segregation at grain boundaries, but when Mo is too high, it will also form coarse carbide is not conducive to H2S stress corrosion performance, so the Mo content is controlled in 0.90-1.10%.

[0056] Ni: Ni is an austenite stabilizing element, with the effect of expanding the phase region, increasing the stability of supercooled austenite, improving the hardenability of steel. At the same time, Ni improves the toughness of the material by solid solution, especially significantly reduces the ductile-brittle transition temperature. And Ni can refine the martensite lath width, improve the strength, but excessive addition reduces the SSC resistance of steel. Therefore, the Ni content is controlled in 0.50%-0.70%.

[0057] V: The role of V in the quenched and tempered steel is to inhibit tempering softening and increase the tempering temperature. VC carbide precipitates at high temperature tempering to play a precipitation strengthening effect, so it ensures that the steel at high temperature tempering reduces the dislocation density and improves the SSC resistance, and also meets the requirement of high strength of 135 ksi; but when the V content in the steel exceeds a certain upper limit, the SSC resistance no longer improves, so the V content is controlled in 0.10-0.20%.

[0058] Nb: can improve the tempering softening resistance of steel, so that the steel obtains good comprehensive mechanical properties. When the content of Nb increases to 0.1%, flat MC carbide precipitates at the grain boundary. When the content of Nb increases further, spherical cementite uniformly precipitates in the grain, which can effectively improve the SSC resistance; but when the Nb content exceeds 0.2%, it may lead to the occurrence of oversized chain and block NbN inclusions during steelmaking, which reduces the performance of the material, so the Nb content is controlled in 0.10%-0.20%.

[0059] Ca / S: In the refining process, Ca wire is added to the steel liquid for calcium treatment. On the one hand, the solid Al2O3 inclusions in the steel are modified into liquid calcium aluminate, improving the castability of the steel liquid during continuous casting. On the other hand, the combination ability of Ca and S is stronger than that of Mn, and point-like CaS inclusions are preferentially generated during the solidification of the steel, which can reduce the total amount and aggregation degree of MnS precipitated in the steel. For low-sulfur steel, Ca / S is in the range of 0.8-2.0, which can form small-size spherical CaS and MnS inclusions, which is beneficial to reduce the generation of long strip-shaped MnS inclusions in the steel, so the Ca / S ratio is controlled in the range of 0.8-2.0.

[0060] P, S and the five harmful elements: P, S and the five harmful elements Sn, Sb, As, Pb, Bi as impurity elements in steel, significantly reduce the material's resistance to SSC performance, should try to reduce their content in steel. P is easy to form segregation in the steel, and MnS inclusion tip stress zone is easy to become the starting point of sulfide stress cracking. Therefore, P, S and the five harmful elements should be controlled at ≤0.010%, ≤0.0015% and ≤0.010% respectively.

[0061] T.O and [N]: oxygen in steel is easy to form oxide inclusions, especially along the rolling direction of class B inclusions, the presence of free nitrogen increases the brittleness of the material, damage the toughness of the material. T.O + [N] total amount should be ≤120ppm.

[0062] In order to ensure the steel better low temperature toughness need to limit the ratio of Si, Mo, Mn, Ni, V, Nb, because Si is easy to gather in the austenite grain boundary, reduce the crystallization binding force, deterioration of low temperature toughness, increase the temper brittleness, so the coefficient of Si is-2.0. Mn can significantly affect the variant selection in the process of phase transformation, increase the variety of phase transformation, thereby improving the low temperature toughness, so the coefficient of Mn is 1.0; Mo can improve the hardenability of steel, can effectively reduce the P, S, As and other impurity elements in the grain boundary, effectively improve the low temperature toughness of steel, so the coefficient of Mo is 1.3; Ni is significantly lower steel toughness transition temperature, improve the low temperature toughness, so the coefficient of Ni is 2.5; Nb, V can precipitate fine MC carbide, refine the organization and improve the temper stability of steel to improve the low temperature toughness, so the coefficient of Nb, V is 2.0:

[0063] That is, T = -2 × % Si + 1.0 × % Mn + 1.3 × % Mo + 2.5 × % Ni + 2.0 × (% V + % Nb) ≥ 3.20%.

[0064] In order to ensure that the steel has good hydrogen sulfide corrosion resistance, the proportioning of Si, Mn, Cr, Mo, Nb and V needs to be limited. Since Si and Mn are easy to segregate at the austenite grain boundary, the crystallization binding force is reduced, the microstructure is non-uniform, and the corrosion resistance is reduced, therefore the coefficient is -5. Mo can improve the hardenability of the steel, effectively reduce the segregation of impurity elements such as P and S at the grain boundary, and precipitate carbide Mo2C during the tempering process, which can become a trap for H, effectively improving the sulfur resistance of the steel, so the coefficient of Mo is 12; Nb and V precipitated MC type carbide can effectively inhibit grain growth, and as an irreversible H trap, greatly improve the SSC resistance, in addition, it can improve the temper softening resistance of the steel, reduce the dislocation density of the material, and improve the SSC resistance. Research shows that the hydrogen trapping capacity of NbC is greater than that of VC, so the coefficient of V is 18, and the coefficient of Nb is 20; The irreversible H hydrogen trap provided by Cr can effectively capture H atoms, slow down the diffusion rate of H atoms, and improve the SSC resistance, so the coefficient of Cr is 10:

[0065] That is, R = -5 x (%Si + %Mn) + 12 x %Mo + 10 x %Cr + 20 x %Nb + 18 x %V ≥ 23.00%.

[0066] The present application adopts Cr-Mo-Ni system and is supplemented with Nb, V and other micro-alloy elements to improve the strength and toughness, and further improve the SSC resistance. The present application reduces the content of C and Mn, increases the content of Ni, Nb and other alloy elements, improves the low temperature impact toughness of the material at -20℃, reduces the dislocation density of the material through two quenching and tempering treatments, and passes the loading strength of NACE TM0177 standard A solution.

[0067] Compared with the prior art, the present application adopts a reasonable component system, pure steel refining control technology and two quenching and tempering processes, which can obtain a dispersed and refined second phase on the tempering sorbite matrix at room temperature, a low dislocation density and a high proportion of low-angle grain boundaries, so that the material has good strength and toughness and excellent hydrogen sulfide corrosion resistance. The present application uses two short-time tempering treatments, the size of the precipitates and the dislocation density are significantly reduced, and the SSC resistance is improved. The product has low proportion of Σ3 boundary, high-angle grain boundary and high Taylor factor value, and the sensitivity of crack initiation and propagation is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0068] Figure 1 It is a metallographic structure diagram of Example 1;

[0069] Figure 2 It is an austenite grain diagram of Example 1. DETAILED DESCRIPTION

[0070] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0071] Embodiments 1-3

[0072] A high-toughness hydrogen sulfide corrosion-resistant drill pipe seamless steel pipe steel comprises the following mass percentage components: as shown in Table 1, and the balance of Table 1 is Fe and unavoidable impurities.

[0073] Comparative Examples 1-3

[0074] A high-toughness hydrogen sulfide corrosion-resistant drill pipe seamless steel pipe steel comprises the following mass percentage components: as shown in Table 1, and the balance of Table 1 is Fe and unavoidable impurities.

[0075] Table 1 Chemical composition of the embodiments of the present application and the comparative examples (wt%)

[0076]

[0077] In Table 1, T.Ca is actual data measured by equipment; and the other five harmful elements Sn, Sb, As, Pb and Bi are controlled at ≤0.010%.

[0078] The production method of the high-toughness hydrogen sulfide corrosion-resistant drill pipe seamless steel pipe steel of each of the above embodiments and the comparative examples is as follows:

[0079] Electric arc furnace smelting→LF furnace refining→RH vacuum degassing→continuous casting→rolling.

[0080] The specific main process is as follows:

[0081] The electric arc furnace smelting: deoxidation and alloying are performed after tapping, and the amount of slag is strictly controlled, the smelting endpoint S≤0.030%, and P≤0.120%.

[0082] The LF furnace refining: C, Si, Mn, Cr, Ni, Mo, V and Nb elements are adjusted to target values, white slag retention time≥20min, and smelting cycle≤70min.

[0083] The RH vacuum degassing: pure degassing time≥25min, soft blowing time≥20min, [H]≤1.0ppm after vacuum treatment, calcium treatment is performed, and the controlled Ca / S of each of the embodiments and the comparative examples is shown in Table 1.

[0084] The continuous casting process involves round billets, with the tundish superheat controlled at 45°C above the liquidus. The billet diameter D and casting speed v should conform to the formula: D = 1029 - 1980 × v - 1470 × v. 2 The unit of the continuous casting billet diameter D is mm, and the unit of the casting speed v is m / min. This invention produces a continuous casting round billet with a diameter D = 500 mm, a superheat of 45 °C, and a casting speed v = 0.23 m / min.

[0085] Rolling: Φ500mm continuously cast round billets are rolled into Φ150mm hot-rolled round bars. The billets are fed into a walking beam furnace, heated to a temperature ≥1230℃, and held for 762 minutes. The diameter (D, mm) of the continuously cast billet and the heating time t (min) should meet the requirement of D=180+0.42t. The initial rolling temperature is ≥1180℃, and the final rolling temperature is 950℃. After rolling, the billets are cooled under an insulation cover or in a slow cooling pit. The finished product is then produced through the above rolling process.

[0086] In the actual production of the steel described in the above embodiments and comparative examples, production can be achieved by controlling the process within the above range.

[0087] The above embodiments and comparative examples of high-strength, tough, hydrogen sulfide corrosion-resistant drills use seamless steel pipes to produce seamless steel pipes, specifically disclosed as follows: hot-rolled round steel → heating → pipe threading → sizing → heat treatment → steel pipe grinding → steel pipe flaw detection → precision machining → flaw detection → packaging and warehousing.

[0088] The specific heat treatment process is as follows:

[0089] Quenching: Heating temperature (W1, ℃) AC3 + 30~50℃, holding time (t1, min) determined by the steel pipe wall thickness (S, mm), t1 = 3.2 × S, water cooling. AC3 was obtained using a Gleeble-2000D thermal simulation testing machine. W1 in all embodiments and comparative examples satisfies W1 = AC3 + 30~50℃.

[0090] Tempering: The primary tempering temperature (W2, ℃) is 650–720℃, and the holding time (t2, min) is determined by the steel pipe wall thickness (S, mm), where t2 = 6 × S. After air cooling to room temperature, a secondary tempering is performed. The secondary tempering temperature (W3, ℃) is W3 = W2 - 10, and the holding time (t3, min) is determined by the steel pipe wall thickness (S, mm), where t3 = 5 × S. Air cooling is then performed.

[0091] The specific heat treatment processes for each embodiment and comparative example are shown in Table 2.

[0092] Table 2 lists the heat treatment processes of the embodiments and comparative examples of the present invention.

[0093]

[0094] The performance testing methods for the steel pipes produced in the above embodiments and comparative examples are as follows:

[0095] Organization: Samples were taken from half the wall thickness of the end cross section of the steel pipe for metallographic and grain size analysis.

[0096] Performance: Tensile, impact, and SSC resistance specimens were taken at 1 / 2 radius of the steel pipe. Mechanical property tests were conducted according to GB / T228 and GB / T229. SSC resistance tests were conducted according to NACE TM0177 standard method A (at a loading strength of 80% SMYS, H2S partial pressure of 0.1 MPa, and temperature of 25℃). Average grain size was observed according to GB / T 6394. The results are shown in Table 3.

[0097] Non-metallic inclusions: Samples were taken from 1 / 2 radius of the hot-rolled round steel and tested according to Method A of ASTM E45. The properties are shown in Table 4.

[0098] Table 3. Performance testing results of embodiments and comparative examples of the present invention.

[0099]

[0100] Table 4 Requirements for Non-metallic Inclusion Levels (Unit: Level)

[0101]

[0102] The chemical composition and production methods of the steels in Examples 1-3 were appropriately controlled, and their chemical compositions met the requirements, resulting in good strength, toughness, and SSC resistance. Comparative Example 1 had a low Ni content, leading to a low R value. Even with production and heat treatment according to the process of this invention, the product's strength, toughness, and SSC resistance would still be reduced. Comparative Example 2, although its composition met the requirements of this invention, did not meet the T value requirements, resulting in low low-temperature toughness and low SSC resistance. Comparative Example 3, although its composition met the requirements of this invention, suffered from improper calcium treatment and heat treatment not performed according to this invention, leading to a significant increase in inclusions and a significant reduction in strength, toughness, and SSC resistance.

[0103] The data underlined above do not meet the requirements of this invention.

[0104] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A seamless steel pipe characterized by, The seamless steel pipe is produced by using the high-toughness hydrogen sulfide corrosion-resistant seamless steel pipe steel; The high-toughness hydrogen sulfide corrosion-resistant seamless steel pipe steel comprises the following components in percentage by mass: Cr: 1.00-1.30%, Ni: 0.50-0.70%, Mo: 0.90-1.10%, Al: 0.020-0.050%, V: 0.10-0.20%, Nb: 0.10-0.20%, C: 0.20-0.25%, Si: 0.15-0.30%, Mn: 0.50-0.70%, P≤0.010%, S≤0.0015%, and the balance of Fe and inevitable impurities; The components of the high-toughness hydrogen sulfide corrosion-resistant seamless steel pipe steel also satisfy T=-2×%Si+1.0×%Mn+1.3×%Mo+2.5×%Ni+2.0×(%V+%Nb)≥3.20%; The components of the high-toughness hydrogen sulfide corrosion-resistant seamless steel pipe steel also satisfy: R=-5×(%Si+%Mn)+12×%Mo+10×%Cr+20×%Nb+18×%V≥23.00%; The seamless steel pipe is produced by using the high-toughness hydrogen sulfide corrosion-resistant seamless steel pipe steel, and the heat treatment process comprises one-time quenching and twice tempering; The quenching is performed at a heating temperature W1=AC3+30-50℃, the holding time t is determined by the pipe wall thickness S, t1=3.2×S, and water cooling is performed after holding; wherein the unit of the heating temperature W1 is ℃, the unit of the holding time t1 is min, and the unit of the pipe wall thickness S is mm; In the twice tempering, the first-time tempering is performed at W2=650-720℃, the holding time t2 is determined by the pipe wall thickness S, t2=6×S, and air cooling is performed to room temperature after holding; The unit of the first-time tempering temperature W2 is ℃, the unit of the holding time t2 is min, and the unit of the pipe wall thickness S is mm; The second-time tempering is performed at W3=W2-10℃, the holding time t3 is determined by the pipe wall thickness S, t3=5×S, and air cooling is performed after holding; The unit of the second-time tempering temperature W3 is ℃, the unit of the holding time t3 is min, and the unit of the pipe wall thickness S is mm.

2. The seamless steel tube according to claim 1, characterized in that, The non-metallic inclusion level of the seamless steel pipe is that the non-metallic A, B, C and D inclusions in the steel are all not greater than 1.0 level, and the total of the A, B, C and D inclusions is not greater than 2.5 level; and the grain size at the 1 / 2 wall thickness of the end cross section of the seamless steel pipe is ≤20μm.

3. The seamless steel tube according to claim 1, characterized in that, The seamless steel pipe has a tensile strength of ≥1050 MPa, a yield strength of ≥940 MPa, an impact energy of ≥110 J at-20 ℃, and a dislocation density of 3.0×10 13 / m -2 ~4.5×10 13 / m -2 ; the seamless steel pipe passes the hydrogen sulfide corrosion resistance test of the American standard NACE TM0177 standard A method at a loading strength of 80% SMYS, a hydrogen sulfide partial pressure of 0.1 MPa, and a temperature of 25 ℃, and does not break after 720 h of testing.

4. The seamless steel tube according to claim 1, characterized in that, The production method of the high-toughness hydrogen sulfide corrosion-resistant seamless steel pipe steel comprises the following technological process: Electric arc furnace smelting→LF furnace refining→RH vacuum degassing→continuous casting→rolling.

5. The seamless steel tube according to claim 4, characterized in that, The RH vacuum degassing is performed by calcium treatment, and the effective calcium-sulfur ratio Ca / S formula is controlled as follows: Ca / S = [T.Ca - (0.31 + 0.02 x T.Ca) x (0.99 x T.O - 5.44)] / (1.25 x T.S); 0.8 < Ca / S < 2.0; wherein T.S is the total sulfur mass fraction in the steel, 10 -6 S < 0.005; T.Ca is the total calcium mass fraction in the steel, 10 -6 Ca < 0.005; T.O is the total oxygen mass fraction in the steel, 10 -6 O < 0.

005.

6. The seamless steel tube according to claim 4, characterized in that, The continuous casting: the diameter D of the continuously cast billet and the casting speed v satisfy D = 1029 - 1980 x v - 1470 x v 2 wherein the diameter D of the continuously cast billet is in mm and the casting speed v is in m / min.

7. The seamless steel tube according to claim 4, characterized in that, The rolling is performed by feeding the casting blank into a walking beam furnace, and the continuous casting blank diameter D and the heating time t satisfy D=180+0.42t, the unit of the continuous casting blank diameter D is mm, and the unit of the heating time t is min.

8. A heat treatment process of the seamless steel tube as set forth in any one of claims 1 to 7, characterized by, The heat treatment process comprises one-time quenching and twice tempering; The quenching: heating temperature W1=AC3+30~50℃, holding time t determined by the pipe wall thickness S, t1=3.2×S, water cooling after holding; wherein the unit of heating temperature W1 is ℃, the unit of holding time t1 is min, the unit of pipe wall thickness S is mm; The first of the two tempering W2 is 650~720℃, holding time t2 determined by the pipe wall thickness S, t2=6×S, air cooling to room temperature after holding; Wherein, the unit of tempering temperature W2 is ℃, the unit of holding time t2 is min, the unit of pipe wall thickness S is mm; The second tempering W3=W2-10℃, holding time t3 determined by the pipe wall thickness S, t3=5×S, air cooling after holding; Wherein, the unit of tempering temperature W3 is ℃, the unit of holding time t3 is min, the unit of pipe wall thickness S is mm.

9. Use of a seamless steel tube as claimed in any one of claims 1-7, characterized in that, For the exploitation of 10,000-meter deep well oilfield.

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