Steel for high-toughness hydrogen sulfide corrosion-resistant seamless steel tube for drilling and production method thereof, seamless steel tube, heat treatment process and application

Abstract

The invention provides high-toughness hydrogen sulfide corrosion-resistant steel for a seamless steel pipe for drilling and production, a production method of the high-toughness hydrogen sulfide corrosion-resistant steel, a seamless steel pipe heat treatment process and application of the high-toughness hydrogen sulfide corrosion-resistant steel. The high-toughness hydrogen sulfide corrosion-resistant steel comprises the following components: 1.00-1.30% of Cr, 0.50-0.70% of Ni, 0.90-1.10% of Mo, 0.020-0.050% of Al, 0.10-0.20% of V, 0.10-0.20% of Nb, 0.20-0.25% of C, 0.15-0.30% of Si, 0.50-0.70% of Mn, less than or equal to 0.010% of P, less than or equal to 0.0015% of S and the balance of Fe and inevitable impurities. A Cr-Mo-Ni system is adopted and supplemented with microalloy elements such as Nb and V to improve the obdurability and improve the SSC resistance. And through two times of thermal refining, the dislocation density of the material is reduced, and the loading strength of a NACE TM0177 standard A solution is met.

Description

Technical Field

[0001] The present invention belongs to the field of alloy steel, and specifically relates to a high-strength and toughness hydrogen sulfide corrosion resistant drill seamless steel pipe steel and its production method, seamless steel pipe and heat treatment process and application, which are suitable for 10,000-meter deep well oil field exploitation. Background Art

[0002] In recent years, with the increasing consumption of petroleum energy, the exploration and development of oil and gas fields are facing the challenges of complex and harsh working conditions such as deep reservoirs, high temperatures, high pressures, and H2S-rich gases. When oil-specific pipes such as oil well pipes are in service in deep wells and ultra-deep well oil fields containing corrosive media such as H2S, they are prone to various corrosion failure phenomena, resulting in reduced oil and gas production, and even oil well safety accidents. This requires oil well pipes to have higher strength and toughness, while also having certain corrosion resistance. At present, 125ksi is the highest level of sulfur-resistant oil well pipe in the API standard. The highest sulfur-resistant level of 125ksi can no longer meet the use requirements, and the development of 135ksi sulfur-resistant oil well pipes is imperative. With the increase in strength, the sensitivity of the material to H2S increases. The development of oil well pipes with both high strength and toughness and high SSC resistance is of great significance to the oil and gas extraction industry.

[0003] At present, many studies are trying to develop 135ksi steel grade sulfur-resistant oil well pipes. However, the developed 135ksi steel grade sulfur-resistant oil well pipes are difficult to meet the index requirements while meeting the toughness requirements and are resistant to H2S corrosion, especially difficult to pass the assessment of NACE TM0177 standard A solution. In addition, the process flow of the oil well pipes in some studies is long and the production efficiency is low. Therefore, it is necessary to consider the chemical composition and process to develop oil well pipes with excellent hydrogen sulfide corrosion resistance and good toughness and their preparation methods to ensure the safe and reliable use of oil well pipes in sulfur-containing deep wells.

[0004] The Chinese patent with publication number CN117821861A published on April 5, 2024, discloses a 125 steel grade anti-sulfur pipe and its preparation method. In the technical solution published in the patent, the main principle is low carbon and supplemented by Cr-Mo-Ni-V-Cu alloy addition, but the technical solution adds more precious metal elements such as Ni, reaching Ni: 1.0-2.0%, and the material cost is relatively high.

[0005] The Chinese patent with publication number CN107177797A published on September 19, 2017 discloses a 130KSI and 135KSI grade corrosion-resistant drill tool steel for oil and gas fields and a manufacturing method thereof. In the technical scheme disclosed therein, the main principle is to improve the hardenability and toughness of the steel by adding main elements such as Mn, Cr, Mo, and to strengthen it by adding trace amounts of V, Nb, Ni, Cu and other elements. After a single quenching and tempering treatment, a tempered bainite structure is obtained. However, its low-temperature Charpy impact energy at -20°C is only greater than 42J, which cannot meet the impact toughness requirements of the drill tool at a depth of 10,000 meters.

[0006] Therefore, it is very necessary to provide a seamless steel pipe for high-strength SSC drill rigs with a steel grade of 135ksi for use in 10,000-meter deep wells. Summary of the invention

[0007] The purpose of the present invention is to provide a high-strength and toughness hydrogen sulfide corrosion resistant drill seamless steel pipe steel and its production method, using Cr-Mo-Ni system supplemented with Nb, V and other micro-alloy elements to improve toughness, and further improve the SSC resistance. By reducing the content of C and Mn and increasing the content of alloying elements such as Ni and Nb, the -20°C low-temperature impact toughness of the material is improved.

[0008] Another object of the present invention is to provide a seamless steel pipe and a heat treatment process, wherein the seamless steel pipe is produced by using the above-mentioned high-strength and toughness hydrogen sulfide corrosion-resistant drill and the steel for seamless steel pipe is used. Through two tempering treatments, the dislocation density of the material is reduced, and the loading strength of the NACE TM0177 standard A solution is higher.

[0009] Another object of the present invention is to provide an application of a seamless steel pipe for use in oil field exploitation at a depth of 10,000 meters.

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

[0011] A high-strength and tough hydrogen sulfide corrosion-resistant drill seamless steel pipe steel includes the following mass percentage components:

[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%, the balance is Fe and inevitable impurities.

[0013] The composition of the seamless steel pipe used in the high-strength and toughness hydrogen sulfide corrosion resistant drill also meets the following requirements:

[0014] T.O+[N]≤120ppm;

[0015] Preferably, the composition of the seamless steel pipe used in the high-toughness and hydrogen sulfide corrosion-resistant drill also satisfies the control of the five harmful elements Sn, Sb, As, Pb, and Bi within ≤0.010%;

[0016] The composition of the seamless steel pipe used in the high-strength and tough hydrogen sulfide corrosion resistant drill also satisfies the following: 0.8≤Ca / S≤2.0; Ca / S=[T.Ca-(0.31+0.02×T.Ca)×(0.99×TO-5.44)] / (1.25×TS).

[0017] The composition of the seamless steel pipe used in the high-strength and toughness hydrogen sulfide corrosion resistant drill also meets the following requirements: 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 used in the high-strength and toughness hydrogen sulfide corrosion resistant drill also meets the following requirements:

[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 present invention provides a method for producing seamless steel pipe steel with high strength and toughness and resistance to hydrogen sulfide corrosion, comprising the following process flow:

[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 is low-sulfur scrap steel and molten pig iron, the steel is deoxidized and alloyed, and the slag amount is strictly controlled. The smelting end point S is less than or equal to 0.030%, and P is less than or equal to 0.120%.

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

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

[0027] [H]≤1.0ppm.

[0028] The calcium treatment of the present invention is an effective means to modify the sulfide morphology in the ingot. The calcium treatment not only modifies the original Al2O3 inclusions in the ingot into liquid calcium aluminate inclusions, but also in the cooling process, Ca preferentially combines with S to form CaS, thereby reducing the precipitation temperature of MnS inclusions and reducing the precipitation amount of MnS inclusions. The Ca / S range is 0.8 to 2.0, and the effective calcium-sulfur ratio Ca / S formula is defined as:

[0029] Ca / S=[T.Ca-(0.31+0.02×T.Ca)×(0.99×TO-5.44)] / (1.25×TS). This is a Ca treatment formula designed for this type of steel. Since the precipitated long strips of sulfides will deteriorate the comprehensive properties of the material, the formula is obtained by thermodynamic calculation fitting of inclusions in the cooling process of the steel ingot through relevant thermodynamic calculation software.

[0030] Where TS is the total sulfur content in steel, 10 -6 , that is, the S content in the steel composition; T.Ca is the total calcium mass fraction in the steel, 10 -6 ; TO is the total oxygen mass fraction in steel, 10 -6 .

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

[0032] Rolling: The billet is sent into a step-beam heating furnace, the heating temperature of the round steel is ≥1230℃, the diameter D of the continuous casting billet and the heating time t should meet D=180+0.42t, the unit of the continuous casting billet diameter D is mm, and the unit of the heating time t is min. The starting rolling temperature is ≥1180℃, the final rolling temperature is 700~950℃, and after rolling, a heat preservation cover is used or the billet is put into a slow cooling pit for slow cooling. The above rolling is finished.

[0033] When calculating, simply substitute the value before the unit into the formula.

[0034] Preferably, the Φ380mm-Φ700mm continuously cast round billets are rolled into Φ90mm-Φ250mm round steels.

[0035] The present invention provides a heat treatment process for a seamless steel pipe, which uses the above-mentioned high-strength and toughness hydrogen sulfide corrosion-resistant drill to produce a seamless steel pipe using steel for a seamless steel pipe. The heat treatment process includes one quenching and two temperings.

[0036] The quenching: heating temperature W1 = AC3 + 30 ~ 50 ° C, the holding time t1 is determined by the steel pipe wall thickness S, t1 = 3.2 × S, and water cooling after holding.

[0037] Among them, the unit of heating temperature W1 is ℃, the unit of holding time t1 is min, and the unit of steel pipe wall thickness S is mm;

[0038] First tempering: The first tempering temperature W2 is 650-720℃, the holding time t2 is determined by the steel pipe wall thickness S, t2=6×S, and air-cooled to room temperature after holding;

[0039] Among them, the unit of the primary tempering temperature W2 is ℃, the unit of the holding time t2 is min, and the unit of the steel pipe wall thickness S is mm;

[0040] Second tempering: Second tempering temperature W3 = W2-10℃, holding time t3 is determined by the steel pipe wall thickness S, t3 = 5×S, air cooling after holding.

[0041] Among them, the unit of secondary tempering temperature W3 is ℃, the unit of holding time t3 is min, and the unit of steel pipe wall thickness S is mm.

[0042] When calculating the above formula, simply substitute the value before the unit into the formula.

[0043] It is hoped that some micro-alloying elements such as Mo, Nb, and V added to the composition of the present invention can be uniformly precipitated during the tempering process to increase strength, refine grains, increase the number of irreversible hydrogen traps, and thus improve sulfur resistance. Secondly, the two temperings can further improve the uneven performance of the organization, reduce stress concentration inside the organization, and more effectively improve the comprehensive mechanical properties of the material.

[0044] A seamless steel pipe is obtained by adopting the above heat treatment process, wherein the grain size at 1 / 2 wall thickness of the end cross section of the seamless steel pipe is ≤20 μm; and the structure is tempered troostite.

[0045] The non-metallic inclusion level of the seamless steel pipe is: the non-metallic A, B, C and D inclusions in the steel are not greater than level 1.0, and the total of A, B, C and D inclusions is not greater than level 2.5.

[0046] Preferably, the level of non-metallic inclusions in the seamless steel pipe after heat treatment is: Class A coarse series 0 level, Class A fine series 0 level, Class B coarse series ≤0.5 level, Class B fine series ≤0.5 level, Class C coarse series 0 level, Class C fine series 0 level, Class D fine series ≤0.5 level, Class D coarse series ≤1.0 level; the sum of all types of inclusions of Class A, Class B, Class C and Class D is ≤2.5 level.

[0047] The room temperature mechanical properties of the seamless steel pipe are tensile strength ≥ 1050 MPa and yield strength ≥ 940 MPa.

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

[0049] The seamless steel pipe passed the hydrogen sulfide corrosion resistance test using the American standard NACE TM0177 standard A method under a loading strength of 80% SMYS, a H2S partial pressure of 0.1 MPa, and a temperature of 25°C, and no fracture occurred during the test for 720 hours.

[0050] The present invention provides an application of a seamless steel pipe, which is produced by the above method and is used for exploitation in a 10,000-meter deep well oil field.

[0051] The main design ideas of the present invention are as follows:

[0052] C: ensures the strength of steel, improves hardenability and thus increases the percentage of martensite transformation; in addition, increasing the C content can increase the number of carbides precipitated during tempering, and these carbides are good H traps: but too high a C content will not only cause segregation itself, but will also greatly increase the segregation of Mn and P, thereby reducing the SSC resistance, so the C content is controlled at 0.20-0.25%.

[0053] Mn: improves the strength and permeability of steel, but Mn is an easily segregated element. Excessive Mn content is easily segregated with S and P at the grain boundaries, so it is not good for the anti-SSC performance. The Cr and Mo contents designed in the present invention are relatively high, which are sufficient to ensure the hardenability and strength of the steel, so the Mn content is controlled at 0.50-0.70%.

[0054] Cr: Improves strength and hardenability, improves corrosion resistance, but excessive Cr content will precipitate large Cr at the grain boundary during tempering 23 C6 carbide is not conducive to the resistance to H2S stress corrosion, so the Cr content is controlled at 1.00-1.30%.

[0055] Mo: It is an important solid solution strengthening and tempering precipitation strengthening element, and it improves the hardenability of steel. Mo carbides precipitate during high temperature tempering to improve tempering resistance, so sufficient Mo must be added to ensure high strength and high tempering temperature. In addition, Mo can also reduce the segregation of P at the grain boundary by reducing the diffusion coefficient of P, but when Mo is too high, coarse carbides will also be formed, which is not conducive to the resistance to H2S stress corrosion, so the Mo content is controlled at 0.90-1.10%.

[0056] Ni: Ni is an austenite stabilizing element, which has the function of expanding the phase region, increasing the stability of supercooled austenite, and improving the hardenability of steel. At the same time, Ni improves the toughness of the material by solid solution, especially significantly reducing the tough-brittle transition temperature. Ni can also refine the width of martensite laths and improve strength, but excessive addition reduces the SSC resistance of steel. Therefore, the Ni content is controlled at 0.50% to 0.70%.

[0057] V: Its role in quenched and tempered steel is to inhibit tempering softening and increase tempering temperature. During high temperature tempering, VC carbides are precipitated to play a precipitation strengthening role, thus ensuring that the dislocation density of the steel is reduced during high temperature tempering, improving the SSC resistance, and ensuring the high strength requirement of 135ksi; however, when the V content in the steel exceeds a certain upper limit, the SSC resistance will no longer be improved, so the V content is controlled at 0.10-0.20%.

[0058] Nb: It can improve the tempering softening resistance of steel and make the steel obtain good comprehensive mechanical properties. When the Nb content increases to 0.1%, the flat MC carbide precipitates at the grain boundary, further increasing the Nb content, and the spherical cementite precipitates evenly in the grain, which can effectively improve the SSC resistance; but if the Nb content exceeds 0.2%, it may lead to the appearance of oversized chain and block NbN inclusions in the steelmaking process, reducing the material properties, so the Nb content is controlled at 0.10% to 0.20%.

[0059] Ca / S: During the refining process, Ca wire is added to treat the molten steel with calcium. On the one hand, the solid Al2O3 inclusions in the steel are modified into liquid calcium aluminates, which improves the castability of the molten steel during the continuous casting process. On the other hand, Ca has a stronger binding ability with S than Mn, and point-like CaS inclusions are preferentially generated during the solidification of molten steel, which can reduce the total amount and aggregation of MnS precipitation in the steel. For low-sulfur steel, when Ca / S is in the range of 0.8 to 2.0, small-sized spherical CaS and MnS inclusions can be formed, which is beneficial to reduce the formation of long strip-shaped MnS inclusions in the steel, so the Ca / S ratio is controlled at 0.8 to 2.0.

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

[0061] TO and [N]: Oxygen in steel easily forms oxide inclusions, especially type B inclusions along the rolling direction. The presence of free nitrogen increases the brittleness of the material and impairs its toughness. The total amount of T.O + [N] should be ≤120ppm.

[0062] In order to ensure good low-temperature toughness of steel, the ratio of Si, Mo, Mn, Ni, V and Nb needs to be limited. Since Si is easy to segregate at the austenite grain boundary, it reduces the crystal bonding force, deteriorates the low-temperature toughness and increases the temper brittleness, so the coefficient of Si is -2.0. Mn can significantly affect the variant selection during the phase transformation process, increase the types of variants in the phase transformation, and thus improve the low-temperature toughness, so the coefficient of Mn is 1.0; Mo can improve the hardenability of steel, effectively reduce the segregation of impurity elements such as P, S, and As at the grain boundary, and effectively improve the low-temperature toughness of steel, so the coefficient of Mo is 1.3; Ni significantly reduces the tough-to-brittle transition temperature of steel and improves low-temperature toughness, so the coefficient of Ni is 2.5; Nb and V can precipitate fine MC carbides, refine the structure and improve the tempering stability of steel, thereby improving the low-temperature toughness, so the coefficients of Nb and V are 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 the steel has good hydrogen sulfide corrosion resistance, the ratio 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 crystal bonding force is reduced, resulting in uneven microstructure and reduced corrosion resistance, so the coefficient is -5. Mo can improve the hardenability of steel, effectively reduce the segregation of impurity elements such as P and S at the grain boundary, and precipitate carbide Mo2C during tempering, which can become a trap for capturing H, effectively improving the sulfur resistance of steel, so the coefficient of Mo is 12; MC-type carbides precipitated by Nb and V can effectively inhibit grain growth, and as irreversible H traps, greatly improve the SSC resistance. In addition, it can improve the steel's resistance to temper softening, reduce the material's dislocation density, and improve the SSC resistance. Studies have shown that NbC has a greater ability to capture hydrogen than 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 anti-SSC performance, so the coefficient of Cr is 10:

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

[0066] The present invention adopts Cr-Mo-Ni system and supplements with micro alloying elements such as Nb and V to improve toughness and further improve SSC resistance. The present invention reduces the content of C and Mn, increases the content of alloying elements such as Ni and Nb, improves the -20°C low-temperature impact toughness of the material, and 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 invention adopts a reasonable component system, a refining control technology of pure steel and a two-time quenching and tempering process, and can obtain a dispersed and refined second phase distributed on the tempered troostite matrix at room temperature, a lower dislocation density and a higher proportion of low-angle grain boundaries, so that the material has good strength and toughness and excellent resistance to hydrogen sulfide corrosion. The present invention uses two short-time tempering treatments, and the size and dislocation density of the precipitate are significantly reduced, thereby improving the SSC resistance. The product has a lower proportion of Σ3 boundaries, high-angle grain boundaries and high Taylor factor values, and the sensitivity to crack initiation and expansion is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 This is the metallographic structure diagram of Example 1;

[0069] Figure 2 This is the austenite grain diagram of Example 1. DETAILED DESCRIPTION

[0070] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0071] Example 1-Example 3

[0072] A high-strength and tough steel for a seamless steel pipe resistant to hydrogen sulfide corrosion includes the following components in percentage by mass: as shown in Table 1, the remainder not shown in Table 1 is Fe and unavoidable impurities.

[0073] Comparative Example 1-Comparative Example 3

[0074] A high-strength and tough steel for a seamless steel pipe resistant to hydrogen sulfide corrosion includes the following components in percentage by mass: as shown in Table 1, the remainder not shown in Table 1 is Fe and unavoidable impurities.

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

[0076]

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

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

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

[0080] The main specific processes are:

[0081] The electric arc furnace smelting: steel is deoxidized and alloyed, and the amount of slag is strictly controlled, and the smelting end point S is ≤ 0.030%, and P is ≤ 0.120%.

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

[0083] The RH vacuum degassing: pure degassing time ≥ 25 min, soft blowing time ≥ 20 min, [H] ≤ 1.0 ppm after vacuum treatment, calcium treatment, the effective calcium-sulfur ratio Ca / S of each embodiment and comparative example is shown in Table 1.

[0084] The continuous casting: round billet continuous casting, the tundish superheat is controlled to be 45°C above the liquidus line, the continuous casting billet diameter D and the drawing speed v should meet D = 1029-1980×v-1470×v 2 The unit of the continuous casting billet diameter D is mm, and the unit of the pulling speed v is m / min. The present invention produces a continuous casting round billet with a diameter of D=500 mm, an overheat of 45°C, and a pulling speed v=0.23 m / min.

[0085] Rolling: Φ500mm continuous casting round billet is rolled into Φ150mm hot-rolled round steel, and the billet is sent into a step-beam heating furnace, and the heating temperature is ≥1230℃, and the holding time is 762min. The continuous casting billet diameter (D, mm) and the heating time t (min) should meet D=180+0.42t. The starting rolling temperature is ≥1180℃, the final rolling temperature is 950℃, and the insulation cover or slow cooling in the slow cooling pit is used after rolling, and the finished product is formed through the above rolling.

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

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

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

[0089] Quenching: Heating temperature (W1, °C) AC3+30~50°C, holding time (t1, min) determined by steel pipe wall thickness (S, mm), t1=3.2×S, water cooling. AC3 is tested using Gleeble-2000D thermal simulation tester. W1 in each embodiment and comparative example satisfies W1=AC3+30~50°C.

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

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

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

[0093]

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

[0095] Organization: Take samples from 1 / 2 wall thickness of the cross section at the end of the steel pipe for metallographic and grain size analysis.

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

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

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

[0099]

[0100] Table 4 Non-metallic inclusion level requirements (unit: level)

[0101]

[0102] The chemical composition and production method of the steel of Examples 1-3 are properly controlled, and their chemical composition meets the requirements, and the strength, toughness and SSC resistance of the steel are good. The Ni content of Comparative Example 1 is relatively low, resulting in a relatively low R value. Even if produced and heat treated according to the process of the present invention, the strength, toughness and SSC resistance of the product will still be reduced. Although the component content of Comparative Example 2 meets the requirements of the present invention, the T value does not meet the requirements of the present invention, resulting in low low-temperature toughness of the product and low SSC resistance. Although the components of Comparative Example 3 meet the requirements of the present invention, the calcium treatment is improper, and the heat treatment is not carried out according to the present invention, resulting in a significant increase in inclusions, and a significant reduction in strength, toughness and SSC resistance.

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

[0104] The description of the above embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and 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 present invention should be within the protection scope of the present invention.

Claims

1. A high-strength and tough drill resistant to hydrogen sulfide corrosion adopts seamless steel pipe steel, characterized in that: The high-strength and toughness hydrogen sulfide corrosion resistant drill adopts the seamless steel pipe steel comprising the following mass percentage components: 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%, the balance is Fe and inevitable impurities.

2. The high-toughness and hydrogen sulfide corrosion-resistant drill according to claim 1 is made of seamless steel pipe steel, characterized in that: The composition of the seamless steel pipe used in the high-toughness and hydrogen sulfide corrosion resistant drill also meets the following requirements: T = -2 ×%Si+1.0×%Mn+1.3×%Mo+2.5×%Ni+2.0×(%V+%Nb)≥3.20%.

3. The high-toughness and hydrogen sulfide corrosion-resistant drill according to claim 1 is made of seamless steel pipe steel, characterized in that: The composition of the seamless steel pipe used in the high-strength and toughness hydrogen sulfide corrosion resistant drill also meets the following requirements: R=-5×(%Si+%Mn)+12×%Mo+10×%Cr+20×%Nb+18×%V≥23.00%.

4. A method for producing seamless steel pipe steel for high-strength and tough hydrogen sulfide corrosion resistant drill according to any one of claims 1 to 3, characterized in that: The production method comprises the following process flow: Electric arc furnace smelting → LF furnace refining → RH vacuum degassing → continuous casting → rolling.

5. The production method according to claim 4, characterized in that: The RH vacuum degassing is performed for calcium treatment, and the effective calcium-sulfur ratio Ca / S is controlled by the formula: Ca / S=[T.Ca-(0.31+0.02×T.Ca)×(0.99×TO-5.44)] / (1.25×TS); 0.8≤Ca / S≤2.0; TS is the total sulfur mass fraction in steel, 10 -6 , that is, the S content in the steel composition; T.Ca is the total calcium mass fraction in the steel, 10 -6 ; TO is the total oxygen mass fraction in steel, 10 -6 .

6. The production method according to claim 4, characterized in that: The continuous casting: the continuous casting billet diameter D and the drawing speed v meet D = 1029-1980×v-1470×v 2 , where the unit of continuous casting billet diameter D is mm, and the unit of casting speed v is m / min.

7. The production method according to claim 4, characterized in that: The rolling process is as follows: the ingot is fed into a walking beam heating furnace, the diameter D of the ingot and the heating time t satisfy D=180+0.42t, the unit of the diameter D of the ingot is mm, and the unit of the heating time t is min.

8. A heat treatment process for a seamless steel pipe, characterized in that: The seamless steel pipe is produced by using the high-strength and toughness hydrogen sulfide corrosion-resistant drill described in any one of claims 1 to 3 and using the steel for seamless steel pipe, characterized in that the heat treatment process includes one quenching and two temperings.

9. The heat treatment process according to claim 8, characterized in that: The quenching: heating temperature W1 = AC3 + 30 ~ 50 ° C, the holding time t is determined by the steel pipe wall thickness S, t1 = 3.2 × S, water cooling after holding; wherein, the unit of the heating temperature W1 is ° C, the unit of the holding time t1 is min, and the unit of the steel pipe wall thickness S is mm.

10. The heat treatment process according to claim 8 or 9, characterized in that: The W2 of the first tempering in the two temperings is 650-720℃, and the holding time t2 is determined by the wall thickness S of the steel pipe, t2=6×S, and air-cooled to room temperature after holding; Among them, the unit of the primary tempering temperature W2 is ℃, the unit of the holding time t2 is min, and the unit of the steel pipe wall thickness S is mm; The second tempering W3 = W2-10 ° C, the holding time t3 is determined by the steel pipe wall thickness S, t3 = 5 × S, and air cooling is performed after holding. Among them, the unit of secondary tempering temperature W3 is ℃, the unit of holding time t3 is min, and the unit of steel pipe wall thickness S is mm.

11. A seamless steel pipe produced by the heat treatment process according to any one of claims 8 to 10, characterized in that: The non-metallic inclusion level of the seamless steel pipe is: the non-metallic inclusions of Class A, Class B, Class C and Class D in the steel are not greater than Class 1.0, and the sum of Class A, Class B, Class C and Class D is not greater than Class 2.5; the grain size at 1 / 2 of the wall thickness of the end cross section of the seamless steel pipe is ≤20μm.

12. The seamless steel pipe according to claim 11, characterized in that: The room temperature mechanical properties of the seamless steel pipe include tensile strength ≥1050MPa, yield strength ≥940MPa, -20℃ impact energy ≥110J, dislocation density ≥3.0×10 13 / m -2 ~4.5×10 13 / m -2 The seamless steel pipe passed the hydrogen sulfide corrosion test using the American standard NACE TM0177 standard A method at a loading strength of 80% SMYS, a H2S partial pressure of 0.1 MPa, and a temperature of 25°C, and no fracture occurred during the test for 720 hours.

13. Use of the seamless steel pipe according to claim 11 or 12, characterized in that: Used for oil field exploitation at a depth of 10,000 meters.

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