High-toughness corrosion-resistant steel and production process thereof

Abstract

The invention relates to the technical field of steel for oil casings, and particularly discloses high-toughness corrosion-resistant steel and a production process thereof. By reducing the contents of C, Cr and Mo, adding the element B and controlling a material distribution process, electric furnace smelting, electric furnace tapping and a refining process, the purity of molten steel is improved, the content of harmful elements (such as P and S) in the molten steel is reduced, the defects of center looseness, middle cracks and the like of a casting blank are reduced, the obdurability and hydrogen sulfide stress corrosion resistance of the steel are remarkably improved, and the service life of the casting blank is prolonged. Reliable guarantee is provided for production of the steel for the high-end oil casing, the urgent requirement of the oil and gas exploitation industry for high-performance steel is effectively met, and high application and popularization value is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of steel for oil casing, and in particular to high-strength, toughness, and corrosion-resistant steel and a production process thereof. Background Art

[0002] In today's energy sector, the efficient and safe extraction of oil and gas resources is increasingly crucial. As key components in oil and gas extraction, the performance of oil casing and tubing directly impacts the success of these operations. 110ksi-grade steel for oil casing and tubing, due to its excellent overall mechanical properties, is widely used in oil and gas well construction. However, as oil and gas extraction expands into deeper, more complex geological areas, higher demands are placed on the quality and performance of oil casing and tubing. Existing 110ksi-grade steel for oil casing and tubing and its production processes have exposed numerous issues that require urgent resolution.

[0003] Existing smelting and continuous casting processes struggle to effectively control the solidification process of molten steel, leading to frequent defects such as center porosity and cracks in the ingot. This center porosity results in a loose internal structure, reducing the steel's load-bearing capacity. Cracks in the center act as stress concentration points, potentially expanding during subsequent rolling and service, leading to the risk of fracture. These defects not only increase scrap rates and production costs during production, but also make it difficult for the final product to meet the stringent safety and reliability requirements of oil and gas wells.

[0004] Furthermore, strength, toughness, and corrosion resistance are core technical bottlenecks that are currently difficult to achieve simultaneously. To improve strength and toughness, existing processes typically employ high-alloying designs, adding large amounts of alloying elements such as Mo, Ni, and V. However, high alloy content can alter the steel's solidification characteristics and phase transformation behavior, exacerbating central porosity and cracking in the ingot. Furthermore, while high alloy content can enhance the steel's strength and toughness to a certain extent, it can also compromise its corrosion resistance, making it unsuitable for the complex corrosive media used in oil and gas production.

[0005] Therefore, developing a production process for 110ksi grade oil casing steel that can achieve synergistic improvement in high strength and toughness and excellent corrosion resistance is of great significance to promoting the sustainable development of the oil and gas extraction industry. Summary of the Invention

[0006] In response to the above problems, the present invention provides a high-strength, toughness, and corrosion-resistant steel and a production process thereof. By reducing the contents of C, Cr, and Mo, adding the element B, and controlling the material distribution process, electric furnace smelting, electric furnace tapping, and refining process, the purity of the molten steel is improved, the content of harmful elements (such as P, S, etc.) in the molten steel is reduced, and the occurrence of defects such as looseness in the center of the ingot and middle cracks is reduced. The strength and toughness and resistance to hydrogen sulfide stress corrosion of the steel are significantly improved, providing reliable technical support for the high-quality development of the oil and gas extraction industry.

[0007] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions: A high-strength, tough, and corrosion-resistant steel, the chemical composition and mass percentage of which are: 0.18%≤C≤0.22%, 0.25%≤Si≤0.35%, 0.50%≤Mn≤0.60%, P≤0.008%, S≤0.0015%, 0.010%≤Al≤0.04%, 0.50%≤Cr≤0.60%, 0.70%≤Mo≤0.75%, 0.01%≤V≤0.15%, 0. 01%≤Ti≤0.02%, 0.0010%≤B≤0.0020%; Sn+As+Pb+Bi+Sb≤0.025%, and the content of each element is ≤0.01%; Cu≤0.1%, Ni≤0.1%, Zn≤0.01%, and Ni+Cu+Zn≤0.20%; O≤20ppm, N≤60ppm, H≤1.5ppm; the balance is Fe and unavoidable impurity elements.

[0008] Compared with the prior art, the high-strength and tough corrosion-resistant steel provided by the present invention reduces the content of C, Cr and Mo, refines the size of the precipitated phase, and inhibits the CrC x 、MoC y The precipitation of large precipitates at grain boundaries improves dendritic and compositional segregation, thereby reducing the formation of banded structures and significantly improving corrosion resistance. Simultaneously, the addition of a small amount of element B, utilizing its segregation at grain boundaries, effectively refines the grains, improving the hardenability and toughness of the steel. Aluminum, acting as a deoxidizer, effectively refines the grains, improves the purity of the molten steel, and ensures the uniformity and density of the steel's internal structure. By controlling the contents of elements such as O, N, and H, the inclusion content in the steel is significantly reduced, lowering the likelihood of defects such as center porosity and cracks in the ingot. Strictly limiting the contents of residual elements such as P, S, Sn, and As reduces the tendency to intergranular corrosion and stress corrosion caused by impurities. Through the synergistic effect of these components, a balance between toughness and corrosion resistance is achieved, meeting the demand for high-performance steel in complex oil and gas production environments and possessing high practical value.

[0009] The high-strength, toughness, and corrosion-resistant steel provided by the present invention effectively breaks through the bottleneck of existing technologies, reduces the content of alloying elements such as Cr and Mo, and achieves a significant improvement in steel performance at a lower production cost, providing reliable technical support for the high-quality development of the oil and gas extraction industry.

[0010] Another aspect of the present invention provides a production process for the above-mentioned high-strength, toughness, and corrosion-resistant steel, comprising an electric furnace smelting process, an electric furnace tapping process, a refining and slag-making process, a VD vacuum refining process, and a continuous casting process; The steelmaking raw materials of the electric furnace smelting process include scrap steel, calcium carbon balls and briquettes; after the smelting is completed, the carbon content in the molten steel is controlled to be 0.06% to 0.09%, the phosphorus content is ≤0.005%, and the w(FeO) in the slag is 15% to 20%, the basicity CaO / SiO2 is 2.5 to 3.0, and the w(CaO) / w(FeO) is 2.0 to 3.5; The electric furnace tapping process includes: adding a pre-deoxidizer when the electric furnace tapping reaches 9% to 11% of the total amount of steel, adding an aluminum ingot when the electric furnace tapping reaches 14% to 16% of the total amount of steel, sequentially adding a silicon manganese alloy, a high carbon ferrochrome, a ferromolybdenum and a vanadium nitrogen alloy when the electric furnace tapping reaches 24% to 26% of the total amount of steel, and adding lime, synthetic slag, fluorite and aluminum flakes when the electric furnace tapping reaches 34% to 36% of the total amount of steel; In the refining and slagging process, the refined slag includes the following components in percentage by mass: CaO 55%~60%, SiO27%~9%, Al2O325%~30%, MgO 4%~6%, FeO+MnO<0.6%, and w(CaO) / w(Al2O3)=1.9~2.1, w(CaO) / w(SiO2)=6.5~7.5.

[0011] Compared with the prior art, the production process of high-strength and tough corrosion-resistant steel provided by the present invention adopts calcium carbon balls to match carbon as steelmaking raw materials, which can not only add carbon to molten steel, but also release calcium to participate in slag formation. The calcium in the calcium carbon balls can react with the oxides in the slag, effectively reducing the oxidizability of the slag, creating favorable conditions for dephosphorization and desulfurization of molten steel, and the use of calcium carbon balls to match carbon not only avoids the limitation of only adding carbon when a single graphite ball is matched with carbon, but also breaks through the process bottleneck of pig iron matching carbon requiring additional slag making. At the same time, the rapid slag-forming characteristics of the calcium carbon balls can prompt the slag to quickly form a high basicity system in the early stage of smelting, thereby removing the phosphorus content to a lower level in the early stage of smelting. In addition, the use of calcium carbon balls instead of pig iron to match carbon can reduce the amount of silicon brought in, reduce the generation of silicon oxide from the source, and reduce the content of residual arsenic. The present invention reduces the oxidation loss of steel materials caused by highly oxidizing slag in traditional processes through the synergistic mechanism of slag making with carbon and controlling oxygen with slag, and effectively reduces the carbon matching cost, which plays a key role in improving the corrosion resistance of steel.

[0012] In the process of tapping steel in an electric furnace, when the tapping volume reaches 9%~11%, a pre-deoxidizer is added to consume part of the oxygen in the molten steel in advance, reduce the oxidizability of the molten steel, create a low-oxygen environment for the subsequent addition of alloy elements, reduce alloy burnout, and improve the alloy yield; when the tapping volume reaches 14%~16%, aluminum ingots are added to further enhance the deoxidation effect, and at the same time, aluminum deoxidation products are used to promote the polymerization and floating of inclusions, thereby improving the purity of the molten steel; when the tapping volume reaches 24%~26%, silicon manganese alloy, high carbon ferrochrome, molybdenum are added in sequence. Iron and vanadium-nitrogen alloys are characterized by excellent molten steel fluidity and a suitable temperature, ensuring full dissolution and uniform composition of the alloying elements while also preventing oxidation loss due to premature addition, thereby increasing alloy yield. The addition of lime, synthetic slag, fluorite, and aluminum flakes at a tapping rate of 34% to 36% rapidly forms a slag with suitable basicity and fluidity, effectively covering the molten steel and preventing secondary oxidation. Furthermore, the alkaline slag reacts with impurities such as sulfur and phosphorus in the molten steel, further removing sulfur and phosphorus, and improving the cleanliness of the molten steel. Precise control of this process significantly reduces alloy consumption and smelting costs while significantly improving the purity and uniformity of the molten steel.

[0013] By precisely controlling the proportions of components such as CaO, SiO2, Al2O3 and key indicators such as w(CaO) / w(Al2O3) and w(CaO) / w(SiO2), a high-basicity, low-oxidizing refining slag system is formed, which combines efficient desulfurization and dephosphorization with excellent fluidity and stability. This is beneficial to ensuring the high purity of molten steel, reducing the generation of sulfur inclusions, and thus improving strength, toughness and resistance to hydrogen sulfide corrosion.

[0014] It should be noted that the briquettes used in the present invention can be commercially available conventional scrap briquettes or scrap steel briquettes, as long as the chemical composition of the briquettes is within the following range: C 0.06%~0.50%, Si 0.15 0.35%, Mn 0.2%~1.8%, Cr0.06%~3%, and the balance is other elements.

[0015] In some embodiments, the specific distribution method in the electric furnace smelting process is: The steelmaking raw materials are distributed in three batches; the first batch accounts for 44% to 46% of the total steelmaking raw materials, the second batch accounts for 32% to 34% of the total steelmaking raw materials, and the third batch accounts for 21% to 23% of the total steelmaking raw materials; Among them, the proportion of scrap steel in primary and secondary cloth is 69%~71%, the proportion of calcium carbon balls is 4%~6%, and the proportion of briquettes is 24%~26%. The proportion of scrap steel in tertiary cloth is 84%~86%, the proportion of calcium carbon balls is 2%~4%, and the proportion of briquettes is 11%~13%.

[0016] By controlling the appropriate pig iron loading, we ensure low-cost smelting while effectively promoting the carbon-oxygen (CO) reaction in the molten steel. During the smelting process, the large number of bubbles generated by the carbon-oxygen reaction not only effectively remove hydrogen and nitrogen from the molten steel but also cause inclusions to float, significantly improving the purity of the molten steel. Through this material distribution process, the nitrogen content of the molten steel entering the LF station has been significantly reduced from an average of 65ppm to 43ppm, providing a strong guarantee for the production of high-quality steel.

[0017] In some embodiments, in each distribution, 49% to 51% of the total amount of carbon calcium balls are distributed at a height of (0.12 to 0.13) h, 29% to 31% are distributed at a height of (0.24 to 0.26) h, and the remainder are distributed at a height of (0.48 to 0.52) h; h is the height of the highest material level of each distribution from the bottom of the tank.

[0018] It should be noted that the above-mentioned calcium carbon ball distribution height refers to the height from the calcium carbon ball distribution position to the bottom of the tank.

[0019] Different ratios of calcium-carbon balls are placed at different heights, leveraging the temperature and fluidity differences of the molten steel from top to bottom. The upper layer (0.12-0.13 h) features high temperature and strong fluidity, allowing a large number of calcium-carbon balls to melt rapidly, accelerating the incorporation of carbon into the molten steel and releasing calcium components, rapidly reducing the oxidizing properties of the slag. The calcium-carbon balls in the middle layer (0.24-0.26 h) supplement the slag alkalinity and promote inclusion adsorption. The remaining calcium-carbon balls in the lower layer (0.48-0.52 h) ensure uniform composition at the bottom of the molten steel, avoiding localized composition fluctuations. The vigorous reaction triggered by the calcium-carbon balls in the upper layer drives convection in the molten steel. The optimized slag in the middle layer continuously adsorbs floating inclusions, while the calcium-carbon balls in the lower layer stabilize the bottom molten steel composition. This distribution of calcium-carbon balls not only ensures a recarburization effect but also significantly reduces the sulfur and oxygen content and inclusion content in the molten steel, improving its purity.

[0020] In some embodiments, the mass percentage of the calcium carbon spheres is: CaO 65%~70%, C 25%~30%, Al2O33%~5%, H2O≤1.5%, and the remainder is unavoidable impurity elements.

[0021] In some embodiments, in terms of mass percentage, among the scrap steel, scrap steel with a thickness of ≥4 mm accounts for 46% to 50%, scrap steel with a thickness of 2 mm to 4 mm accounts for 48% to 52%, and the remainder is scrap steel with a thickness of less than 2 mm.

[0022] In some embodiments, the length of the scrap steel is ≤800 mm and the width is ≤800 mm.

[0023] In some embodiments, the thickness of the pressing block is 0.8 mm to 1.2 mm.

[0024] In some embodiments, the length, width and height of the compact are all ≤1000 mm.

[0025] In some embodiments, the arc smelting process includes the following steps: After the first batch of material is laid, power is supplied to smelt and the oxygen supply intensity is maintained at 0.4Nm 3 / min·t~0.6Nm 3 / min·t, when the primary charge is melted 80%~85%, the power is cut off for secondary charge distribution, and the power is turned on for smelting, maintaining the oxygen supply intensity at 0.4Nm 3 / min·t~0.6Nm 3 / min·t, when the secondary charge is melted 85%~90%, the power is cut off for the third batch of charge, and the power is turned on for smelting, while the oxygen supply intensity is maintained at 0.4Nm 3 / min·t~0.6Nm 3 / min·t, and maintain the oxygen supply intensity at 0.6Nm after smelting for 10min~12min 3 / min·t~0.8Nm 3 / min·t, until steel is tapped.

[0026] Low-intensity oxygen supply is used during the first charging stage to suppress premature and violent carbon-oxygen reactions and maintain a low-temperature environment in the molten pool. Oxygen supply is continued after the second and third charging stages to trigger a violent carbon-oxygen reaction, releasing CO bubbles, which drives strong stirring of the molten pool, accelerates the diffusion of sulfur elements to the slag-steel interface, and improves desulfurization efficiency. At the same time, the boiling effect generated by the carbon-oxygen reaction effectively removes hydrogen and nitrogen from the molten steel, achieving a synergistic "decarbonization-desulfurization-degassing" effect.

[0027] It should be noted that the electric furnace adopts a constant power mode throughout the power supply process, and the output power is overloaded by 15%~20% according to the rated power of the transformer.

[0028] In some embodiments, after a cloth is laid, the power supply voltage is 812V and the current is 50470A~50570A within 2 minutes of power supply; the power supply voltage is 864V and the current is 47430A~47530A within 2 minutes of power supply; after 5 minutes of power supply, the power supply voltage is 890V and the current is 46040A~460140A; After the second cloth, the power supply voltage is 812V and the current is 50470A~50570A within 2 minutes of power supply; the power supply voltage is 864V and the current is 47430A~47530A within 2 minutes of power supply; after 4 minutes of power supply, the power supply voltage is 890V and the current is 46040A~460140A; After three times of laying, within 2 minutes of power supply, the supply voltage is 812V and the current is 50470A~50570A; within 2 minutes of power supply, the supply voltage is 864V and the current is 47430A~47530A; after 4 minutes of power supply, the supply voltage is 890V and the current is 46040A~460140A.

[0029] The above smelting process can make the slag system stable and have a strong dephosphorization efficiency. By controlling the oxygen supply intensity, the appropriate key carbon content of steel can be met under the conditions of all scrap steel smelting.

[0030] In some embodiments, in the electric furnace steel-tapping process, the chemical composition and mass percentage of the pre-deoxidizer are: Al 22%~25%, Al2O3 20%~22%, CaO 25%~27%, Si 8%~9%, and the balance is other elements.

[0031] In some embodiments, the synthetic slag includes the following components in percentage by weight: Al2O3 45% to 50%, CaO 32% to 40%, SiO2 4% to 10%, MgO < 3%, and the balance being other elements.

[0032] In some embodiments, during the electric furnace tapping process, the amount of the pre-deoxidizer added is 0.4 kg / t to 0.6 kg / t.

[0033] In some embodiments, the amount of the aluminum ingot added is 1.9 kg / t to 2.1 kg / t.

[0034] In some embodiments, the amount of lime added is 5.5kg / t~6.5kg / t, the amount of synthetic slag added is 3.4kg / t~3.6kg / t, the amount of fluorite added is 3.2kg / t~3.4kg / t, and the amount of aluminum flake added is 0.4kg / t~0.6kg / t.

[0035] In some embodiments, the refining and slagging process specifically includes the following steps: After 1min~3min of power supply, deoxidizer is added for deoxidation. After 10min~12min of power supply, the steel liquid temperature is 1590℃~1600℃, sampling is taken for testing, and the alloy composition is adjusted to meet the design requirements. According to the results of the refined slag sample, the refined slag composition is adjusted to meet CaO 55%~60%, SiO27%~9%, Al2O325%~30%, MgO 4%~6%, FeO+MnO<0.6%, and w(CaO) / w(Al2O3)=1.9~2.1, w(CaO) / w(SiO2)=6.5~7.5.

[0036] In some embodiments, in the refining and slag making process, the deoxidizer includes calcium carbide and aluminum particles, the amount of calcium carbide added is 0.6kg / t~0.8kg / t, and the amount of aluminum particles added is 0.4kg / t~0.6kg / t.

[0037] In some embodiments, the VD vacuum refining process specifically includes the following steps: Remove 60%~70% of the refining slag, and then carry out VD vacuum refining. When the vacuum degree is 10kPa~100kPa, the argon blowing amount is 40NL / min~60NL / min; when the vacuum degree is 5kPa~10kPa, the argon blowing amount is 60NL / min~100NL / min; when the vacuum degree is 500Pa~5kPa, the argon blowing amount is 100NL / min~140NL / min; when the vacuum degree is 67Pa~500Pa, the argon blowing amount is 140NL / min~160 NL / min; when the vacuum degree is ≤67Pa, first maintain the argon blowing rate at 160NL / min~200NL / min for 15min~17min, then reduce the argon blowing rate to 100NL / min~120NL / min, maintain for 3min~5min, break the air, control the argon blowing rate to 5NL / min~10NL / min, add titanium iron 5min~7min after breaking the air, break the air for 10min~12min, add ferroboron, and enter the next process 20min~22min after breaking the air.

[0038] In some embodiments, the amount of ferrotitanium added is 0.3 kg / t to 0.4 kg / t, and the amount of ferroboron added is 0.02 kg / t to 0.04 kg / t.

[0039] By controlling the amount of argon blowing at different vacuum levels, not only can slag rolling be effectively prevented, but a more ideal degassing effect can also be achieved.

[0040] In some embodiments, during the continuous casting process, a cooling water flow rate is 1.2m 3 / t~1.4m 3 / t, the secondary cooling water flow rate is 0.32m 3 / t~0.34m 3 / t, the crystallizer electromagnetic stirring current is 350A~400A, the frequency is 3Hz~5Hz, the end electromagnetic stirring current is 350A~390A, the frequency is 7Hz~9Hz, the superheat is 20℃~25℃, and the pulling speed is 1.2m / min~2.2m / min.

[0041] By controlling the cooling rate and electromagnetic stirring parameters, the internal microstructure of the ingot can be effectively improved. The electromagnetic force generated by electromagnetic stirring forces the molten steel to flow within the ingot. This flow breaks off the tips of columnar crystals, inhibiting their continued growth. The broken tips then melt in the liquid core, absorbing the superheat of the molten steel and promoting a more uniform temperature distribution in the liquid core. Simultaneously, some tips, acting as nuclei for equiaxed crystal growth, proliferate in the center of the ingot, significantly expanding the equiaxed crystal zone. With the increase in the equiaxed crystal zone, the compositional segregation of the molten steel during solidification is effectively suppressed, especially the degree of central segregation, which in turn reduces defects such as central porosity and shrinkage cavities in the ingot. This significantly improves the equiaxed crystal ratio of the ingot, laying a solid foundation for the production of high-quality steel.

[0042] In summary, the present invention reduces the occurrence of defects such as looseness in the center of the ingot and middle cracks through composition optimization and process control, significantly improves the strength and toughness of the steel and its resistance to hydrogen sulfide stress corrosion, provides reliable guarantees for the production of high-end oil casing steel, effectively meets the urgent demand for high-performance steel in the oil and gas extraction industry, and has high promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a low-magnification photograph of the continuous casting slab prepared in Example 1 of the present invention; Figure 2 This is the metallographic structure diagram of the 110ksi steel grade sulfur-resistant product prepared in Example 1 of the present invention; Figure 3 This is the metallographic structure diagram of the 110ksi steel grade sulfur-resistant product prepared in Comparative Example 1 of the present invention; Figure 4 This is a photo of the inclusion morphology prepared in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0045] In order to better illustrate the present invention, further examples are given below.

[0046] The mass percentages of the calcium carbon spheres used in the following examples are: CaO 65%-70%, C 25%-30%, Al2O33%-5%, H2O≤1.5%, and the remainder are unavoidable impurity elements.

[0047] Among the scrap steel used: scrap steel with a thickness of ≥4mm accounts for 46%~50%, scrap steel with a thickness of 2mm~4mm accounts for 48%~52%, and the remainder is scrap steel with a thickness of less than 2mm. The length of the scrap steel is ≤800mm and the width is ≤800mm.

[0048] The thickness of the pressed block used is 0.8 mm to 1.2 mm, and the length, width, and height of the pressed block are all ≤ 1000 mm. The chemical composition and mass percentage of the pressed block are: C 0.06% to 0.50%, Si 0.15 0.35%, Mn 0.2% to 1.8%, Cr 0.06% to 3%, and the balance is other elements.

[0049] The chemical composition and mass percentage of the pre-deoxidizer used are: Al 22%~25%, Al2O3 20%~22%, CaO 25%~27%, Si 8%~9%, and the balance is other elements.

[0050] The synthetic slag used includes the following components in percentage by mass: Al2O3 45%~50%, CaO 32%~40%, SiO2 4%~10%, MgO <3%, and the balance is other elements.

[0051] The Al content of the aluminum sheet used is ≥98%. The Al content of the aluminum ingot is ≥99%.

[0052] The electric furnace power supply process adopts constant power mode throughout, and the output power is overloaded by 15~20% according to the rated power of the transformer. The 5th gear voltage is 812V, the current is 50520±50A, the 3rd gear is 864V, the current is 47480±50A, and the 2nd gear is 890V, the current is 46090±50A.

[0053] Example 1 The embodiment of the present invention provides a 110ksi steel grade steel for oil casing, the chemical composition and mass percentage of which are as follows: C 0.20%, Si 0.26%, Mn 0.55%, P 0.007%, S 0.0011%, Al 0.025%, Cr 0.55%, Mo0.72%, V 0.13%, Ti 0.015%, B 0.0015%; Sn+As+Pb+Bi+Sb≤0.012%, and the content of each element is ≤0.01%; Cu≤0.1%, Ni≤0.1%, Zn≤0.01%, and Ni+Cu+Zn≤0.20%; O 9ppm, N 43ppm, H 0.8ppm; the balance is Fe and unavoidable impurity elements.

[0054] The production process of the above-mentioned 110ksi steel grade oil casing steel includes the following steps: S1, scrap steel distribution: The total steel material loading is 90t, which is divided into three loading times: the first loading is 40t, including 28t of scrap steel, 10t of briquettes, and 2t of calcium carbon balls; the second loading is 30t, including 21t of scrap steel, 7.5t of briquettes, and 1.5t of calcium carbon balls; the third loading is 20t, including 17t of scrap steel, 2.4t of briquettes, and 0.6t of calcium carbon balls; in each loading, 50% of the total amount of carbon calcium balls is laid at a height of 1 / 8h, 30% is laid at a height of 1 / 4h, and the rest is laid at a height of 1 / 2h; h is the height of the highest material level of each loading from the bottom of the tank; S2, electric furnace smelting: after the primary material is loaded, power supply is in level 5 for 2 minutes, level 3 for 2 to 5 minutes, and level 2 after 5 minutes, and the oxygen supply intensity is maintained at 0.42Nm 3 / min·t, when the primary charge is melted to 82%, the power is turned off and the secondary charge is added. After the secondary charge is added, the power is supplied at level 5 within 2 minutes, level 3 for 2 to 4 minutes, and level 2 after 4 minutes, and the oxygen supply intensity is maintained at 0.42Nm 3 / min·t, when the secondary charge is 87% melted, the power is turned off to add the tertiary charge. After the tertiary charge is added, the power is supplied at level 5 within 2 minutes, level 3 for 2 to 4 minutes, and level 2 after 4 minutes, and the oxygen supply intensity is maintained at 0.43Nm 3 / min·t, and the oxygen supply intensity was maintained at 0.62Nm after smelting for 10min. 3 / min·t, sampling was performed when the molten steel temperature was 1580℃, and the steel was tapped when the P content in the molten steel in the electric furnace was 0.0046% and the C content was 0.064%. At this time, the w(FeO) in the slag was 17%, the basicity CaO / SiO2 was 2.6, and the w(CaO) / w(FeO) was 2.2; S3, electric furnace tapping, the total amount of electric furnace tapping is 85t / furnace, when the electric furnace tapping reaches 10% of the total amount, add pre-deoxidizer, when the electric furnace tapping reaches 15% of the total amount, add 2.0kg / t aluminum ingot; when the electric furnace tapping reaches 25% of the total amount, add silicon manganese alloy, high carbon ferrochrome, ferromolybdenum and vanadium nitrogen alloy in sequence, when the electric furnace tapping reaches 35%, add 6kg / t lime, 3.5kg / t synthetic slag, 3.3kg / t fluorite and 0.5kg / t aluminum flake; S4, refining and slag making: after power supply for 1 minute, add 0.7kg / t of calcium carbide and 0.5kg / t of aluminum particles. After power supply for 12 minutes, the temperature of the molten steel is 1590℃, sampling and testing are carried out, and the alloy composition is adjusted to meet the design requirements. According to the results of the refined slag sample, the refined slag composition is adjusted to meet the requirements of CaO 56%, SiO2 7.5%, Al2O3 27%, MgO 5%, FeO+MnO 0.4%, and w(CaO) / w(Al2O3)=2.07, w(CaO) / w(SiO2)=7.47; S5, VD vacuum refining: remove 66% of the refining slag, then carry out VD vacuum refining. When the vacuum degree is 10kPa~100kPa, the argon blowing rate is 45NL / min; when the vacuum degree is 5kPa~10kPa, the argon blowing rate is 70NL / min; when the vacuum degree is 500Pa~5kPa, the argon blowing rate is 120NL / min; when the vacuum degree is 67Pa~500Pa, the argon blowing rate is 150NL / min; when the vacuum degree is ≤67Pa, first maintain the argon blowing rate of 180NL / min for 15 minutes, then reduce the argon blowing rate to 100NL / min, maintain for 4 minutes, break the air, control the argon blowing rate to 8NL / min, add 0.35kg / t ferrotitanium 5 minutes after breaking the air, add 0.028kg / t ferroboron 10 minutes after breaking the air, and enter the next process 20 minutes after breaking the air. The ferroboron yield is 78%; S6, continuous casting process: The continuous casting process adopts secondary cooling with crystallizer electromagnetic stirring and end electromagnetic stirring, among which the flow rate of primary cooling water is 1.22m 3 / t, the secondary cooling water flow rate is 0.33m 3 / t, the crystallizer electromagnetic stirring current is 380A, the frequency is 4Hz, the end electromagnetic stirring current is 370A, the frequency is 8Hz, the superheat is 23℃, and the pulling speed is 2.0m / min.

[0055] The continuous casting billet prepared in this embodiment was tested according to the YB / T 4149-2018 continuous casting round tube billet detection and judgment method. The detection results of the center porosity, shrinkage cavity, center crack, middle crack, subcutaneous crack, subcutaneous bubble and equiaxed grain of the continuous casting billet are shown in Table 1 and Table 2. Figure 1 shown.

[0056] Table 1

[0057] Note: The traditional steelmaking process refers to the EAF-LF-VD-CC process. In the electric furnace smelting process, all-steel materials are used for smelting, of which scrap steel is 76~80%, briquette is 20~22%, microcrystalline blocks are carbonized 1~1.5%, lime is used for slag making, and the amount of lime added is 23~30kg / t steel. The rest of the operations are the same as in Example 1. In the electric furnace tapping process, no pre-deoxidizer is used for pre-deoxidation, no aluminum sheet is used for slag surface deoxidation, and the timing of adding specific materials is not controlled. The rest of the operations are the same as in Example 1. The slag system of the refining process requires CaO 50%~55%, SiO27%~9%, Al2O320%~27%, MgO 4%~6%, FeO+MnO<1%, w(CaO) / w(SiO2)=6.0~7.0, and the rest of the operation steps are the same as in Example 1. No slag is removed during the VD smelting process, and the argon flow rate of the entire VD process is constant at 70NL / min. The rest of the operations are the same as in Example 1. The flow rate of cooling water in the continuous casting process is 1.4m 3 / t~1.6m 3 / t, the secondary cooling water flow rate is 0.35m 3 / t~0.37m 3 / t, the superheat degree is 20℃~30℃, and the other operating steps are the same as those in Example 1.

[0058] After conventional ring furnace heating, piercing, rolling, micro-tension reducing, straightening, finishing, quenching and tempering, 110ksi steel grade sulfur-resistant product is obtained. Its metallographic structure is shown in the figure below. Figure 2 As shown, the grain size of the organization is 11.0.

[0059] The rolled products were sampled and tested according to GB / T 10561-2023, as shown in Table 2.

[0060] Table 2

[0061] Example 2 The embodiment of the present invention provides a 110ksi steel grade steel for oil casing, the chemical composition and mass percentage of which are as follows: C 0.18%, Si 0.25%, Mn 0.50%, P 0.008%, S 0.0013%, Al 0.010%, Cr 0.50%, Mo0.70%, V 0.15%, Ti 0.01%, B 0.0020%; Sn+As+Pb+Bi+Sb≤0.016%, and the content of each element is ≤0.01%; Cu≤0.1%, Ni≤0.1%, Zn≤0.01%, and Ni+Cu+Zn≤0.20%; O 11ppm, N 56ppm, H 1.4ppm; the balance is Fe and unavoidable impurity elements.

[0062] The production process of the above-mentioned 110ksi steel grade oil casing steel includes the following steps: S1, scrap steel distribution: The total steel material loading is 90t, which is divided into three loading times: the first loading is 40t, including 28t of scrap steel, 10t of briquettes, and 2t of calcium carbon balls; the second loading is 30t, including 21t of scrap steel, 7.5t of briquettes, and 1.5t of calcium carbon balls; the third loading is 20t, including 17t of scrap steel, 2.4t of briquettes, and 0.6t of calcium carbon balls; in each loading, 50% of the total amount of carbon calcium balls is laid at a height of 1 / 8h, 30% is laid at a height of 1 / 4h, and the rest is laid at a height of 1 / 2h; h is the height of the highest material level of each loading from the bottom of the tank; S2, electric furnace smelting: after the primary material is loaded, power supply is in level 5 for 2 minutes, level 3 for 2 to 5 minutes, and level 2 after 5 minutes, and the oxygen supply intensity is maintained at 0.5Nm 3 / min·t, when the primary charge is melted 80%, the power is turned off and the secondary charge is added. After the secondary charge is loaded, the power is supplied at level 5 within 2 minutes, level 3 for 2 to 4 minutes, and level 2 after 4 minutes, and the oxygen supply intensity is maintained at 0.51Nm 3 / min·t, when the secondary charge is 85% melted, the power is turned off to add the tertiary charge. After the tertiary charge is added, the power is supplied at level 5 within 2 minutes, level 3 for 2 to 4 minutes, and level 2 after 4 minutes, and the oxygen supply intensity is maintained at 0.52Nm 3 / min·t, and after smelting for 11 minutes, the oxygen supply intensity was maintained at 0.71Nm 3 / min·t, sampling was performed when the molten steel temperature was 1580℃, and the steel was tapped when the P content in the molten steel in the electric furnace was 0.0047% and the C content was 0.063%; at this time, the w(FeO) in the slag was 16%, the basicity CaO / SiO2 was 2.6, and the w(CaO) / w(FeO) was 2.6; S3, electric furnace tapping, the total amount of electric furnace tapping is 84t / furnace, when the electric furnace tapping reaches 9% of the total amount, pre-deoxidizer is added, when the electric furnace tapping reaches 14% of the total amount, 1.9kg / t aluminum ingot is added; when the electric furnace tapping reaches 24% of the total amount, silicon manganese alloy, high carbon ferrochrome, ferromolybdenum and vanadium nitrogen alloy are added in sequence, when the electric furnace tapping reaches 34%, 5.5kg / t lime, 3.2kg / t synthetic slag, 3.4kg / t fluorite and 0.4kg / t aluminum flake are added; S4, refining and slag making: after power supply for 1 minute, add 0.6kg / t of calcium carbide and 0.4kg / t of aluminum particles. After power supply for 11 minutes, the molten steel temperature reaches 1600℃, and sampling is carried out for testing. The alloy composition is adjusted to meet the design requirements. According to the results of the refined slag sample, the refined slag composition is adjusted to meet the requirements of CaO 57%, SiO2 8.2%, Al2O3 28%, MgO 4.3%, FeO+MnO 0.5%, and w(CaO) / w(Al2O3)=2.05, w(CaO) / w(SiO2)=7.39; S5, VD vacuum refining: remove 60% of the refining slag, then carry out VD vacuum refining. When the vacuum degree is 10kPa~100kPa, the argon blowing rate is 40NL / min; when the vacuum degree is 5kPa~10kPa, the argon blowing rate is 60NL / min; when the vacuum degree is 500Pa~5kPa, the argon blowing rate is 100NL / min; when the vacuum degree is 67Pa~500Pa, the argon blowing rate is 140NL / min; when the vacuum degree is ≤67Pa, first maintain the argon blowing rate of 160NL / min for 17 minutes, then reduce the argon blowing rate to 110NL / min, maintain for 3 minutes, break the vacuum, control the argon blowing rate to 5NL / min, add 0.3kg / t ferrotitanium 6 minutes after breaking the vacuum, add 0.023kg / t ferroboron 11 minutes after breaking the vacuum, and enter the next process 21 minutes after breaking the vacuum. The ferroboron yield is 77%; S6, continuous casting process: The continuous casting process adopts secondary cooling with crystallizer electromagnetic stirring and end electromagnetic stirring, among which the flow rate of primary cooling water is 1.3m 3 / t, the secondary cooling water flow rate is 0.32m 3 / t, the crystallizer electromagnetic stirring current is 360A, the frequency is 3Hz, the end electromagnetic stirring current is 370A, the frequency is 7Hz, the superheat is 20℃, and the pulling speed is 1.3m / min.

[0063] Example 3 The embodiment of the present invention provides a 110ksi steel grade steel for oil casing, the chemical composition and mass percentage of which are as follows: C 0.22%, Si 0.35%, Mn 0.60%, P 0.007%, S 0.0014%, Al 0.04%, Cr 0.60%, Mo0.75%, V 0.01%, Ti 0.02%, B 0.0010%; Sn+As+Pb+Bi+Sb=0.021%, and the content of each element is ≤0.01%; Cu≤0.1%, Ni≤0.1%, Zn≤0.01%, and Ni+Cu+Zn≤0.20%; O 13ppm, N 49ppm, H 1.1ppm; the balance is Fe and unavoidable impurity elements.

[0064] The production process of the above-mentioned 110ksi steel grade oil casing steel includes the following steps: S1, scrap steel distribution: The total steel material loading is 90t, which is divided into three loading times: the first loading is 40t, including 28t of scrap steel, 10t of briquettes, and 2t of calcium carbon balls; the second loading is 30t, including 21t of scrap steel, 7.5t of briquettes, and 1.5t of calcium carbon balls; the third loading is 20t, including 17t of scrap steel, 2.4t of briquettes, and 0.6t of calcium carbon balls; in each loading, 50% of the total amount of carbon calcium balls is laid at a height of 1 / 8h, 30% is laid at a height of 1 / 4h, and the rest is laid at a height of 1 / 2h; h is the height of the highest material level of each loading from the bottom of the tank; S2, electric furnace smelting: after the primary material is loaded, power supply is in level 5 for 2 minutes, level 3 for 2 to 5 minutes, and level 2 after 5 minutes, and the oxygen supply intensity is maintained at 0.58Nm 3 / min·t, when the primary charge is melted 85%, the power is turned off and the secondary charge is added. After the secondary charge is loaded, the power is supplied at level 5 within 2 minutes, level 3 for 2 to 4 minutes, and level 2 after 4 minutes, and the oxygen supply intensity is maintained at 0.57Nm 3 / min·t, when the secondary charge is melted 90%, the power is turned off to add the tertiary charge. After the tertiary charge is added, the power is supplied at level 5 within 2 minutes, level 3 for 2 to 4 minutes, and level 2 after 4 minutes, and the oxygen supply intensity is maintained at 0.58Nm 3 / min·t, and the oxygen supply intensity was maintained at 0.78Nm after smelting for 12min. 3 / min·t, sampling was performed when the molten steel temperature was 1580℃, and the steel was tapped when the P content in the molten steel in the electric furnace was 0.0048% and the C content was 0.061%. At this time, the w(FeO) in the slag was 19%, the basicity CaO / SiO2 was 2.7, and the w(CaO) / w(FeO) was 3.1; S3, electric furnace tapping, the total amount of electric furnace tapping is 87t / furnace, when the electric furnace tapping reaches 11% of the total amount, pre-deoxidizer is added, when the electric furnace tapping reaches 16% of the total amount, 2.1kg / t aluminum ingot is added; when the electric furnace tapping reaches 26% of the total amount, silicon manganese alloy, high carbon ferrochrome, ferromolybdenum and vanadium nitrogen alloy are added in sequence, when the electric furnace tapping reaches 36%, 6.5kg / t lime, 3.4kg / t synthetic slag, 3.6kg / t fluorite and 0.6kg / t aluminum flake are added; S4, refining and slag making: after supplying power for 2 minutes, add 0.8kg / t of calcium carbide and 0.6kg / t of aluminum particles. After supplying power for 10 minutes, the temperature of the molten steel is 1590℃, sampling and testing are carried out, and the alloy composition is adjusted to meet the design requirements. According to the results of the refined slag sample, the refined slag composition is adjusted to meet the requirements of CaO 58%, SiO2 8.6%, Al2O3 28%, MgO 5.7%, FeO+MnO 0.5%, and w(CaO) / w(Al2O3)=2.03, w(CaO) / w(SiO2)=7.41; S5, VD vacuum refining: remove 70% of the refining slag, then carry out VD vacuum refining. When the vacuum degree is 10kPa~100kPa, the argon blowing rate is 60NL / min; when the vacuum degree is 5kPa~10kPa, the argon blowing rate is 100NL / min; when the vacuum degree is 500Pa~5kPa, the argon blowing rate is 140NL / min; when the vacuum degree is 67Pa~500Pa, the argon blowing rate is 160NL / min; when the vacuum degree is ≤67Pa, first maintain the argon blowing rate at 200NL / min for 15min, then reduce the argon blowing rate to 120NL / min, maintain for 5min, break the vacuum, control the argon blowing rate to 10NL / min, add 0.4kg / t ferrotitanium 7min after breaking the vacuum, add 0.04kg / t ferroboron 10min~12min after breaking the vacuum, and enter the next process 22min after breaking the vacuum. The ferroboron yield is 78%; S6, continuous casting process: The continuous casting process adopts secondary cooling with crystallizer electromagnetic stirring and end electromagnetic stirring, among which the flow rate of primary cooling water is 1.4m 3 / t, the secondary cooling water flow rate is 0.34m 3 / t, the crystallizer electromagnetic stirring current is 400A, the frequency is 5Hz, the end electromagnetic stirring current is 390A, the frequency is 9Hz, the superheat is 25℃, and the pulling speed is 2.1m / min.

[0065] The highest inclusion level of the 110 ksi steel-grade sulfur-resistant products prepared in Examples 2 and 3 is 0.5.

[0066] The 110 ksi steel-grade sulfur-resistant products prepared in Examples 1 to 3 were subjected to mechanical property testing according to ISO 6892-1:2019, and SSC testing was performed according to NACE TM0177-2016. The products showed a yield strength of 850-860 MPa, a tensile strength of 880-900 MPa, an elongation of 27%-30%, and a longitudinal full-scale impact energy (0°C) of 220-225 J. They also exhibited excellent hydrogen sulfide stress corrosion resistance, with a 98% pass rate for SSC A-method testing after 720 hours of exposure to liquid A, and a 96% pass rate for 1000 hours.

[0067] Comparative Example 1 This comparative example provides a 110 ksi steel grade oil casing steel, which is different from Example 1 only in that its chemical composition does not contain the B element, that is, no ferroboron is added during the VD vacuum refining process.

[0068] After conventional ring furnace heating, piercing, rolling, micro-tension reducing, straightening, finishing, quenching and tempering, 110ksi steel grade sulfur-resistant product is obtained. Its metallographic structure is shown in the figure below. Figure 3 As shown, the grain size of the organization is 8.5.

[0069] The continuous casting billet prepared in this comparative example was tested according to the YB / T 4149-2018 continuous casting round tube billet detection and judgment method. The test results of the center porosity, shrinkage cavity, center crack, middle crack, subcutaneous crack, subcutaneous bubble and equiaxed grain of the continuous casting billet are shown in Table 3.

[0070] Table 3

[0071] The inclusions are shown in Table 4.

[0072] Table 4

[0073] The product prepared in this comparative example has a yield strength of 750 MPa, a tensile strength of 823 MPa, an elongation of 25%, and a pass rate of 94% for remaining unbroken under SSC A method A liquid for 720 hours. The yield strength does not meet the requirements (the standard minimum is 750 MPa).

[0074] Comparative Example 2 This comparative example provides a 110 ksi steel grade oil casing steel. The only difference from Example 1 is that graphite balls are used instead of calcium carbon balls in the scrap steel material, and lime is added to slag during the electric furnace smelting process. The specific steps are as follows: S1, scrap steel distribution: The total steel material loading is 90t, which is divided into three loadings: the primary loading is 40t, including 29.5t of scrap steel, 10t of briquettes, and 0.5t of graphite balls; the secondary loading is 30t, including 22t of scrap steel, 7.5t of briquettes, and 0.5t of graphite balls; the tertiary loading is 20t, including 17t of scrap steel and 3t of briquettes; S2, after the primary material is loaded, power on for 5 minutes and add 45kg / t of lime into the furnace while maintaining the oxygen supply intensity at 0.42Nm 3 / t, when the primary charge is 80% melted, the power is turned off and the secondary charge is added. After the secondary charge is loaded, the power is turned on and smelted for 4 minutes. 15kg / t of lime is added to the furnace, and the oxygen supply intensity is maintained at 0.42Nm³ / min·t. When the secondary charge is 87% melted, the power is turned off and the tertiary charge is added, and the oxygen supply intensity is maintained at 0.43Nm³ / min·t. 3 / min·t, and the oxygen supply intensity was maintained at 0.62Nm after smelting for 10min. 3 / min·t, sampling was performed when the molten steel temperature was 1580℃, and the P content in the electric furnace molten steel was 0.016%, which failed to achieve the requirement of reducing the P content to below 0.005%; S3~S6: Same as Example 1.

[0075] The impact performance test of the product obtained by heating, piercing, rolling, micro-tension reducing, straightening, finishing, quenching and tempering the continuous casting billet prepared as described above failed, and the longitudinal full-size impact energy (0°C) was 88J (the standard requires more than 100J).

[0076] Comparative Example 3 This comparative example provides a 110ksi steel grade oil casing steel. The only difference from Example 1 is that the addition of aluminum flakes when the steel is tapped to 34% is omitted. The rest is identical. The specific steps are as follows: S1-S2, same as in Example 1; S3, electric furnace tapping: The total amount of steel tapped from the electric furnace is 84t / furnace. When the tapping reaches 9% of the total amount, a pre-deoxidizer is added. When the tapping reaches 14% of the total amount, 1.9kg / t of aluminum ingot is added. When the tapping reaches 24% of the total amount, silicon-manganese alloy, high-carbon ferrochrome, ferromolybdenum and vanadium-nitrogen alloy are added in sequence. When the tapping reaches 34%, 5.5kg / t of lime, 3.2kg / t of synthetic slag and 3.4kg / t of fluorite are added. S4~S6: Same as Example 1.

[0077] The content of FeO+MnO in the refined slag after S4 refining and slagging is 1.2%, and the inclusion content is relatively high after rolling, such as Figure 4 shown.

[0078] The highest inclusion grade was 2.5, which affected the SCC pass rate. The final SCC hanging test resulted in fracture after only 96 hours.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-strength, tough, and corrosion-resistant steel, characterized in that: Its chemical composition and mass percentage are: 0.18%≤C≤0.22%, 0.25%≤Si≤0.35%, 0.50%≤Mn≤0.60%, P≤0.008%, S≤0.0015%, 0.010%≤Al≤0.04%, 0.50%≤Cr≤0.60%, 0.70%≤Mo≤0.75%, 0.01%≤V≤0.15%, 0.01%≤Ti≤0.02%, 0.0010%≤B≤0.0020%; Sn+As+Pb+Bi+Sb≤0.025%, and the content of each element is ≤0.01%; Cu≤0.1%, Ni≤0.1%, Zn≤0.01%, and Ni+Cu+Zn≤0.20%; O≤15ppm, N≤60ppm, H≤1.5ppm; the balance is Fe and unavoidable impurity elements; The production process of the high-strength, tough and corrosion-resistant steel includes an electric furnace smelting process, an electric furnace tapping process, a refining and slag making process, a VD vacuum refining process and a continuous casting process; The steelmaking raw materials of the electric furnace smelting process include scrap steel, calcium carbon balls and briquettes; after the smelting is completed, the carbon content in the molten steel is controlled to be 0.06% to 0.09%, the phosphorus content is ≤0.005%, and the w(FeO) in the slag is 15% to 20%, the basicity CaO / SiO2 is 2.5 to 3.0, and the w(CaO) / w(FeO) is 2.0 to 3.5; The electric furnace tapping process includes: adding a pre-deoxidizer when the electric furnace tapping reaches 9% to 11% of the total amount of steel, adding an aluminum ingot when the electric furnace tapping reaches 14% to 16% of the total amount of steel, sequentially adding a silicon manganese alloy, a high carbon ferrochrome, a ferromolybdenum and a vanadium nitrogen alloy when the electric furnace tapping reaches 24% to 26% of the total amount of steel, and adding lime, synthetic slag, fluorite and aluminum flakes when the electric furnace tapping reaches 34% to 36% of the total amount of steel; In the refining and slagging process, the refined slag includes the following components in percentage by mass: CaO 55%-60%, SiO2 7%-9%, Al2O3 25%-30%, MgO 4%-6%, FeO+MnO<0.6%, and w(CaO) / w(Al2O3)=1.9-2.1, w(CaO) / w(SiO2)=6.5-7.

5.

2. A production process for the high-strength, toughness, and corrosion-resistant steel according to claim 1, characterized in that: Including electric furnace smelting process, electric furnace tapping process, refining and slag making process, VD vacuum refining process and continuous casting process; The steelmaking raw materials of the electric furnace smelting process include scrap steel, calcium carbon balls and briquettes; after the smelting is completed, the carbon content in the molten steel is controlled to be 0.06% to 0.09%, the phosphorus content is ≤0.005%, and the w(FeO) in the slag is 15% to 20%, the basicity CaO / SiO2 is 2.5 to 3.0, and the w(CaO) / w(FeO) is 2.0 to 3.5; The electric furnace tapping process includes: adding a pre-deoxidizer when the electric furnace tapping reaches 9% to 11% of the total amount of steel, adding an aluminum ingot when the electric furnace tapping reaches 14% to 16% of the total amount of steel, sequentially adding a silicon manganese alloy, a high carbon ferrochrome, a ferromolybdenum and a vanadium nitrogen alloy when the electric furnace tapping reaches 24% to 26% of the total amount of steel, and adding lime, synthetic slag, fluorite and aluminum flakes when the electric furnace tapping reaches 34% to 36% of the total amount of steel; In the refining and slagging process, the refined slag includes the following components in percentage by mass: CaO 55%-60%, SiO2 7%-9%, Al2O3 25%-30%, MgO 4%-6%, FeO+MnO<0.6%, and w(CaO) / w(Al2O3)=1.9-2.1, w(CaO) / w(SiO2)=6.5-7.

5.

3. The production process of high-strength and tough corrosion-resistant steel according to claim 2, characterized in that: The specific distribution method in the electric furnace smelting process is: The steelmaking raw materials are distributed in three batches; the first batch accounts for 44% to 46% of the total steelmaking raw materials, the second batch accounts for 32% to 34% of the total steelmaking raw materials, and the third batch accounts for 21% to 23% of the total steelmaking raw materials; Among them, the proportion of scrap steel in primary and secondary cloth is 69%~71%, the proportion of calcium carbon balls is 4%~6%, and the proportion of briquette is 24%~26%. The proportion of scrap steel in tertiary cloth is 84%~86%, the proportion of calcium carbon balls is 2%~4%, and the proportion of briquette is 11%~13%. In each distribution, 49%~51% of the total amount of carbon calcium balls are distributed at a height of 0.12h~0.13h, 29%~31% are distributed at a height of 0.24h~0.26h, and the remainder are distributed at a height of 0.48h~0.52h; h is the height of the highest material level from the bottom of the tank each time.

4. The production process of high-strength, toughness, and corrosion-resistant steel according to claim 2 or 3, characterized in that: The mass percentage of the calcium carbon spheres is: CaO 65%~70%, C 25%~30%, Al2O3 3%~5%, H2O≤1.5%, and the balance is unavoidable impurity elements; and / or Calculated by mass percentage, of the scrap steel, 46% to 50% is scrap steel with a thickness of 4mm or greater, 48% to 52% is scrap steel with a thickness of 2mm to 4mm, and the remainder is scrap steel with a thickness of less than 2mm; and / or The thickness of the pressing block is 0.8 mm to 1.2 mm.

5. The production process of high-strength, toughness, and corrosion-resistant steel according to claim 3, characterized in that: The specific steps of the electric furnace smelting process include: After the first batch of material is laid, power is supplied to smelt and the oxygen supply intensity is maintained at 0.4Nm 3 / min·t~0.6Nm 3 / min·t, when the primary charge is melted 80%~85%, the power is cut off for secondary charge distribution, and the power is turned on for smelting, maintaining the oxygen supply intensity at 0.4Nm 3 / min·t~0.6Nm 3 / min·t, when the secondary charge is melted 85%~90%, the power is cut off for the third batch of charge, and the power is turned on for smelting, while the oxygen supply intensity is maintained at 0.4Nm 3 / min·t~0.6Nm 3 / min·t, and maintain the oxygen supply intensity at 0.6Nm after smelting for 10min~12min 3 / min·t~0.8Nm 3 / min·t, until steel is tapped.

6. The production process of high-strength and tough corrosion-resistant steel according to claim 5, characterized in that: After one cloth is laid, the power supply voltage is 812V and the current is 50470A~50570A within 2 minutes of power supply; the power supply voltage is 864V and the current is 47430A~47530A within 2 minutes of power supply; after 5 minutes of power supply, the power supply voltage is 890V and the current is 46040A~460140A; After the second cloth, the power supply voltage is 812V and the current is 50470A~50570A within 2 minutes of power supply; the power supply voltage is 864V and the current is 47430A~47530A within 2 minutes of power supply; after 4 minutes of power supply, the power supply voltage is 890V and the current is 46040A~460140A; After three times of laying, within 2 minutes of power supply, the supply voltage is 812V and the current is 50470A~50570A; within 2 minutes of power supply, the supply voltage is 864V and the current is 47430A~47530A; after 4 minutes of power supply, the supply voltage is 890V and the current is 46040A~460140A.

7. The production process of high-strength, toughness, and corrosion-resistant steel according to claim 2, characterized in that: In the electric furnace tapping process, the chemical composition and mass percentage of the pre-deoxidizer are: Al 22%-25%, Al2O3 20%-22%, CaO 25%-27%, Si 8%-9%, and the balance is other elements; and / or The synthetic slag includes the following components in percentage by mass: Al2O3 45%-50%, CaO 32%-40%, SiO2 4%-10%, MgO <3%, and the balance being other elements.

8. The production process of high-strength, toughness, and corrosion-resistant steel according to claim 2, characterized in that: In the electric furnace tapping process, the amount of the pre-deoxidizer added is 0.4kg / t to 0.6kg / t; and / or The amount of the aluminum ingot added is 1.9 kg / t to 2.1 kg / t; and / or The amount of lime added is 5.5kg / t~6.5kg / t, the amount of synthetic slag added is 3.4kg / t~3.6kg / t, the amount of fluorite added is 3.2kg / t~3.4kg / t, and the amount of aluminum flake added is 0.4kg / t~0.6kg / t.

9. The production process of high-strength, toughness, and corrosion-resistant steel according to claim 2, characterized in that: The VD vacuum refining process specifically includes the following steps: Remove 60%~70% of the refining slag, and then carry out VD vacuum refining. When the vacuum degree is 10kPa~100kPa, the argon blowing amount is 40NL / min~60NL / min; when the vacuum degree is 5kPa~10kPa, the argon blowing amount is 60NL / min~100NL / min; when the vacuum degree is 500Pa~5kPa, the argon blowing amount is 100NL / min~140NL / min; when the vacuum degree is 67Pa~500Pa, the argon blowing amount is 140NL / min~160 NL / min; when the vacuum degree is ≤67Pa, first maintain the argon blowing rate at 160NL / min~200NL / min for 15min~17min, then reduce the argon blowing rate to 100NL / min~120NL / min, maintain for 3min~5min, break the air, control the argon blowing rate to 5NL / min~10NL / min, add titanium iron 5min~7min after breaking the air, add ferroboron 10min~12min after breaking the air, and enter the next process 20min~22min after breaking the air.

10. The production process of high-strength, toughness, and corrosion-resistant steel according to claim 2, characterized in that: During the continuous casting process, the flow rate of a cooling water is 1.2m 3 / t~1.4m 3 / t, the secondary cooling water flow rate is 0.32m 3 / t~0.34m 3 / t, the crystallizer electromagnetic stirring current is 350A~400A, the frequency is 3Hz~5Hz, the end electromagnetic stirring current is 350A~390A, the frequency is 7Hz~9Hz, the superheat is 20℃~25℃, and the pulling speed is 1.2m / min~2.2m / min.

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