A high-strength and tough corrosion-resistant steel and its production process

Abstract

This invention relates to the field of steel technology for oil casing, specifically disclosing a high-strength, tough, and corrosion-resistant steel and its production process. By reducing the content of C, Cr, and Mo, adding B, and controlling the charge-laying process, electric furnace smelting, electric furnace tapping, and refining processes, this invention improves the purity of molten steel, reduces the content of harmful elements (such as P and S) in the molten steel, and reduces defects such as central porosity and intermediate cracks in the cast billet. This significantly improves the steel's strength, toughness, and resistance to hydrogen sulfide stress corrosion, providing a reliable guarantee for the production of high-end oil casing steel. It effectively meets the urgent demand of the oil and gas extraction industry for high-performance steel and has high application value.

Description

Technical Field

[0001] This invention relates to the field of steel technology for oil casing, and in particular to a high-strength, high-toughness, corrosion-resistant steel and its production process. Background Technology

[0002] In today's energy sector, the efficient and safe extraction of oil and gas resources is increasingly important. As a key component in oil and gas extraction, the performance of casing and tubing directly affects the success or failure of extraction operations. 110ksi grade casing and tubing steel, due to its excellent comprehensive mechanical properties, is widely used in oil and gas well construction. However, as oil and gas extraction expands into deeper and more complex geological areas, higher demands are placed on the quality and performance of casing and tubing. Existing 110ksi grade casing and tubing steel and its manufacturing processes have revealed many problems that urgently need to be addressed.

[0003] Existing smelting and continuous casting processes struggle to effectively control the solidification process of molten steel, leading to frequent defects such as central porosity and intermediate cracks in the cast billet. Central porosity results in a less dense internal structure of the steel, reducing its load-bearing capacity; intermediate cracks become stress concentration points, potentially expanding further during subsequent rolling and service, increasing the risk of fracture. These defects not only increase the scrap rate and production costs but also make it difficult for the final product to meet the stringent safety and reliability requirements of oil and gas wells for casing and tubing.

[0004] In addition, strength, toughness, and corrosion resistance are also core technical bottlenecks that are currently difficult to achieve simultaneously. To improve strength and toughness, existing processes usually adopt high alloying designs, adding large amounts of alloying elements such as Mo, Ni, and V. However, high alloy content will change the solidification characteristics and phase transformation behavior of steel, exacerbating the porosity and cracking tendency in the center of the billet. At the same time, although high alloy composition can enhance the strength and toughness of steel to a certain extent, it may affect its corrosion resistance and make it unable to withstand the erosion of complex corrosive media in oil and gas extraction.

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

[0006] To address the aforementioned problems, this invention provides a high-strength, tough, and corrosion-resistant steel and its production process. By reducing the content of C, Cr, and Mo, adding B element, and controlling the material placement 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 and S) in the molten steel is reduced, and the generation of defects such as central porosity and intermediate cracks in the billet is reduced. This significantly improves the strength, toughness, and resistance to hydrogen sulfide stress corrosion, providing reliable technical support for the high-quality development of the oil and gas extraction industry.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] A high-strength, high-toughness, and corrosion-resistant steel has the following chemical composition and mass percentage: 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. 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.

[0009] Compared to existing technologies, the high-strength, high-toughness, and corrosion-resistant steel provided by this invention reduces the content of C, Cr, and Mo, refines the size of precipitated phases, and inhibits CrC. x MoC y The precipitation of large particles 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 boron (B) utilizes its segregation effect at grain boundaries to effectively refine grains, improving hardenability and toughness. Aluminum, as a deoxidizer, effectively refines grains, improves the purity of molten steel, and ensures the uniformity and density of the internal structure. By controlling the content of elements such as oxygen (O), nitrogen (N), and hydrogen (H), the content of inclusions in the steel is significantly reduced, lowering the probability of defects such as central porosity and intermediate cracks in the billet. Strictly limiting the content of residual elements such as phosphorus (P), sulfur (S), and sn and aspartate arsenic (Sn) reduces the tendency for 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 extraction environments, and possessing high practical value.

[0010] The high-strength, high-toughness, and corrosion-resistant steel provided by this invention effectively breaks through the existing technical bottlenecks, 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.

[0011] Another aspect of the present invention provides a production process for the above-mentioned high-strength, high-toughness, and corrosion-resistant steel, including 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;

[0012] The steelmaking raw materials for the electric furnace smelting process include scrap steel, calcium carbon balls, and briquettes; the C content in the molten steel after smelting is controlled to be 0.06%~0.09%, the P content to be ≤0.005%, and the w(FeO) in the slag to be 15%~20%, the basicity CaO / SiO2 to be 2.5~3.0, and the w(CaO) / w(FeO) to be 2.0~3.5.

[0013] The electric arc furnace tapping process includes: when the electric arc furnace taps steel to 9%~11% of the total amount, adding a pre-deoxidizer; when the electric arc furnace taps steel to 14%~16% of the total amount, adding aluminum ingots; when the electric arc furnace taps steel to 24%~26% of the total amount, sequentially adding silicon-manganese alloy, high-carbon ferrochrome, ferromolybdenum and vanadium-nitrogen alloy; and when the electric arc furnace taps steel to 34%~36% of the total amount, adding lime, synthetic slag, fluorite and aluminum flakes.

[0014] In the refining slag-making process, the refining slag includes the following components by mass percentage: 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.

[0015] Compared to existing technologies, the production process for high-strength, tough, and corrosion-resistant steel provided by this invention utilizes calcium-carbon spheres for carbon addition in steelmaking. This not only increases carbon content in the molten steel but also releases calcium elements to participate in slag formation. The calcium in the calcium-carbon spheres reacts with oxides in the slag, effectively reducing its oxidizing properties and creating favorable conditions for dephosphorization and desulfurization of the molten steel. Using calcium-carbon spheres avoids the limitation of simply adding carbon with graphite spheres and overcomes the bottleneck of requiring additional slag formation when using pig iron for carbon addition. Simultaneously, the rapid slag-forming characteristics of calcium-carbon spheres promote the rapid formation of a high-alkalinity system in the slag during the early stages of smelting, thereby reducing phosphorus content to a lower level in the early stages of smelting. Furthermore, using calcium-carbon spheres instead of pig iron for carbon addition reduces the amount of silicon introduced, reducing silicon oxide formation at the source and decreasing the content of residual arsenic. This invention, through a synergistic mechanism of carbon-based slag formation and slag-based oxygen control, reduces the oxidation loss of steel materials caused by highly oxidizing slag in traditional processes and effectively lowers carbon addition costs, playing a crucial role in improving the corrosion resistance of steel.

[0016] In the electric arc furnace steelmaking process, a pre-deoxidizer is added when the steel yield reaches 9%~11%. This pre-consumes some of the oxygen in the molten steel, reducing its oxidizing properties and creating a low-oxygen environment for subsequent alloying element additions, thus reducing alloy burn-off and increasing alloy yield. When the steel yield reaches 14%~16%, aluminum ingots are added to further enhance the deoxidation effect. Simultaneously, the aluminum deoxidation products promote the aggregation and flotation of inclusions, improving the purity of the molten steel. When the steel yield reaches 24%~26%, silicon-manganese alloy, high-carbon ferrochrome, and molybdenum are added sequentially. For the iron-vanadium-nitrogen alloy, the molten steel has good fluidity and the temperature is suitable at this stage, ensuring that the alloying elements are fully melted and the composition is uniform, while avoiding oxidation and loss of the alloy due to premature addition, thus improving the alloy yield. Adding lime, synthetic slag, fluorite, and aluminum flakes when the steel yield is 34%–36% rapidly forms a slag with suitable basicity and fluidity, effectively covering the molten steel and preventing secondary oxidation. Simultaneously, the alkaline slag reacts with impurities such as sulfur and phosphorus in the molten steel, further desulfurizing and dephosphorizing, improving the cleanliness of the molten steel. Through precise control of this process, not only is alloy consumption and smelting costs significantly reduced, but the purity and compositional uniformity of the molten steel are also greatly improved.

[0017] By precisely controlling the proportions of components such as CaO, SiO2, and Al2O3, as well as key indicators such as w(CaO) / w(Al2O3) and w(CaO) / w(SiO2), a high-basicity, low-oxidizing refining slag system is formed. This system combines efficient desulfurization and dephosphorization with excellent fluidity and stability, which helps ensure high purity of molten steel, reduce the generation of sulfur inclusions, and thus improve strength, toughness, and resistance to hydrogen sulfide corrosion.

[0018] It should be noted that the briquettes used in this 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%, Cr 0.06%~3%, with the balance being other elements.

[0019] In some embodiments, the specific material distribution method in the electric furnace smelting process is as follows:

[0020] The steelmaking raw materials are distributed in three stages; the first distribution accounts for 44% to 46% of the total steelmaking raw materials, the second distribution accounts for 32% to 34% of the total steelmaking raw materials, and the third distribution accounts for 21% to 23% of the total steelmaking raw materials.

[0021] In the primary and secondary feeding processes, scrap steel accounts for 69% to 71%, calcium carbon balls account for 4% to 6%, and briquettes account for 24% to 26%. In the tertiary feeding process, scrap steel accounts for 84% to 86%, calcium carbon balls account for 2% to 4%, and briquettes account for 11% to 13%.

[0022] By controlling the appropriate amount of pig iron added, low-cost smelting can be ensured while effectively promoting the full 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 H and N from the molten steel but also carry inclusions to the surface, significantly improving the purity of the molten steel. Through the above-mentioned feedstock distribution process, the nitrogen content of the molten steel entering the LF station was significantly reduced from an average of 65 ppm to 43 ppm, providing a strong guarantee for the production of high-quality steel.

[0023] In some embodiments, during each feeding, 49% to 51% of the total amount of calcium carbon balls are fed at a height of (0.12 to 0.13)h, 29% to 31% are fed at a height of (0.24 to 0.26)h, and the remainder is fed at a height of (0.48 to 0.52)h; h is the height of the highest material level of each feeding from the bottom of the tank.

[0024] It should be noted that the fabric height of the calcium carbon balls mentioned above refers to the height of the calcium carbon ball fabric position from the bottom of the tank.

[0025] Different proportions of calcium-carbon spheres are placed at different heights to fully utilize the temperature and fluidity differences of molten steel from top to bottom. The upper layer (0.12~0.13 h) has a high temperature and strong fluidity, allowing a large number of calcium-carbon spheres to melt rapidly, accelerating the incorporation of carbon into the molten steel and releasing calcium components, thus quickly reducing the oxidizability of the slag. The calcium-carbon spheres in the middle layer (0.24~0.26 h) supplement and adjust the slag basicity, promoting the adsorption of inclusions. The remaining calcium-carbon spheres in the lower layer (0.48~0.52 h) ensure uniform composition of the molten steel at the bottom, avoiding localized fluctuations. The intense reaction triggered by the upper layer calcium-carbon spheres drives steel convection, the optimized slag from the middle layer calcium-carbon spheres continuously adsorbs floating inclusions, and the lower layer calcium-carbon spheres stabilize the composition of the molten steel at the bottom. This method of calcium-carbon sphere placement not only ensures carbon enrichment but also significantly reduces the content of S and O elements and inclusions in the molten steel, improving the purity of the steel.

[0026] In some embodiments, the mass percentage of the calcium carbon spheres is: CaO 65%~70%, C 25%~30%, Al2O3 3%~5%, H2O≤1.5%, with the balance being unavoidable impurity elements.

[0027] In some embodiments, by mass percentage, the scrap steel comprises: 46% to 50% scrap steel with a thickness of ≥4mm, 48% to 52% scrap steel with a thickness of 2mm to 4mm, and the remainder is scrap steel with a thickness of less than 2mm.

[0028] In some embodiments, the length of the scrap steel is ≤800mm and the width is ≤800mm.

[0029] In some embodiments, the thickness of the pressure block is 0.8 mm to 1.2 mm.

[0030] In some embodiments, the length, width, and height of the pressure block are all ≤1000mm.

[0031] In some embodiments, the specific steps of the electric arc smelting process include:

[0032] After the fabric is laid, it is smelted by electricity, maintaining an oxygen supply intensity of 0.4 Nm. 3 / min·t~0.6Nm 3 / min·t, when the primary charge has melted 80%~85%, power is cut off for secondary charging, then power is restored for smelting, maintaining an oxygen supply intensity of 0.4Nm. 3 / min·t~0.6Nm 3 / min·t, when the secondary furnace charge has melted 85%~90%, power is cut off for a third charging operation, followed by power restoration for smelting, while maintaining an oxygen supply intensity of 0.4Nm. 3 / min·t~0.6Nm 3 / min·t, after smelting for 10-12 minutes, maintain an oxygen supply intensity of 0.6 Nm. 3 / min·t~0.8Nm 3 / min·t, until steel is tapped.

[0033] Low-intensity oxygen supply during the first charging stage inhibits premature and violent carbon-oxygen reaction and maintains a low-temperature environment in the molten pool. After the second and third charging stages, oxygen supply continues, triggering a violent carbon-oxygen reaction that releases CO bubbles, driving intense stirring in the molten pool, accelerating the diffusion of sulfur to the slag-steel interface, and improving 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 effect of "decarburization-desulfurization-degassing".

[0034] It should be noted that the electric furnace is powered in constant power mode throughout the entire process, and the output power is based on the transformer's rated power overload of 15% to 20%.

[0035] In some embodiments, after one fabric application, within 2 minutes of power supply, the supply voltage is 812V and the current is 50470A~50570A; from 2 minutes to 5 minutes of power supply, the supply voltage is 864V and the current is 47430A~47530A; after 5 minutes of power supply, the supply voltage is 890V and the current is 46040A~460140A.

[0036] After the second fabric application, within 2 minutes of power supply, the supply voltage is 812V and the current is 50470A~50570A; from 2 minutes to 4 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.

[0037] After three fabric applications, within 2 minutes of power supply, the supply voltage was 812V and the current was 50470A~50570A; from 2 minutes to 4 minutes of power supply, the supply voltage was 864V and the current was 47430A~47530A; after 4 minutes of power supply, the supply voltage was 890V and the current was 46040A~460140A.

[0038] The above smelting process can stabilize the slag system, achieve strong dephosphorization efficiency, and, by controlling the oxygen supply intensity, meet the appropriate carbon content requirements for tapping steel under all-scrap steel smelting conditions.

[0039] In some embodiments, during 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%, with the balance being other elements.

[0040] In some embodiments, the synthetic slag comprises the following components by mass percentage: Al2O3 45%~50%, CaO 32%~40%, SiO2 4%~10%, MgO <3%, with the balance being other elements.

[0041] In some embodiments, during the electric furnace tapping process, the amount of pre-deoxidizer added is 0.4 kg / t to 0.6 kg / t.

[0042] In some embodiments, the amount of aluminum ingot added is 1.9 kg / t to 2.1 kg / t.

[0043] In some embodiments, the amount of lime added is 5.5 kg / t to 6.5 kg / t, the amount of synthetic slag added is 3.4 kg / t to 3.6 kg / t, the amount of fluorite added is 3.2 kg / t to 3.4 kg / t, and the amount of aluminum sheet added is 0.4 kg / t to 0.6 kg / t.

[0044] In some embodiments, the refining slag-forming process specifically includes the following steps:

[0045] After 1-3 minutes of power supply, deoxidizer is added for deoxidation. After 10-12 minutes of power supply, the temperature of the molten steel reaches 1590℃-1600℃. Samples are taken for testing, and the alloy composition is adjusted to meet the design requirements. Based on the results of the refining slag sample, the composition of the refining slag is adjusted to meet the following requirements: 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.

[0046] In some embodiments, in the refining and slag-forming process, the deoxidizer includes calcium carbide and aluminum granules, with the amount of calcium carbide added being 0.6 kg / t to 0.8 kg / t and the amount of aluminum granules added being 0.4 kg / t to 0.6 kg / t.

[0047] In some embodiments, the VD vacuum refining process specifically includes the following steps:

[0048] Remove 60%~70% of the refining slag, then perform VD vacuum refining. When the vacuum degree is 10kPa~100kPa, the argon blowing rate is 40NL / min~60NL / min; when the vacuum degree is 5kPa~10kPa, the argon blowing rate is 60NL / min~100NL / min; when the vacuum degree is 500Pa~5kPa, the argon blowing rate is 100NL / min~140NL / min; when the vacuum degree is 67Pa~500Pa, the argon blowing rate is 140NL / min~160NL / min. 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 and maintain it for 3min~5min, break the vacuum, control the argon blowing rate at 5NL / min~10NL / min, add ferrotitanium 5min~7min after breaking the vacuum, add ferroboron 10min~12min after breaking the vacuum, and proceed to the next process 20min~22min after breaking the vacuum.

[0049] 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.

[0050] By controlling the amount of argon blown at different vacuum levels, not only can slag entrapment be effectively prevented, but also a more ideal degassing effect can be achieved.

[0051] In some embodiments, the flow rate of the cooling water in the continuous casting process is 1.2 m³ / s. 3 / t~1.4m 3 / t, the secondary cooling water flow rate is 0.32m³ / t. 3 / t~0.34m 3 / t, the electromagnetic stirring current of the crystallizer is 350A~400A, the frequency is 3Hz~5Hz, the electromagnetic stirring current at the end is 350A~390A, the frequency is 7Hz~9Hz, the superheat is 20℃~25℃, and the pulling speed is 1.2m / min~2.2m / min.

[0052] By controlling the cooling rate and electromagnetic stirring parameters, the internal microstructure of the billet can be effectively improved. The electromagnetic force generated by the stirring forces the molten steel to flow within the billet. This flow breaks off columnar crystal tips, inhibiting their continued growth. The broken tips melt in the liquid core, absorbing the superheat of the molten steel, thus promoting a more uniform temperature distribution in the liquid core. Simultaneously, some of these tips act as nuclei for equiaxed crystal growth, multiplying extensively in the central region of the billet and significantly expanding the equiaxed crystal zone. With the increase in the equiaxed crystal zone, compositional segregation during solidification is effectively suppressed, especially at the center, significantly reducing the degree of segregation. This reduces defects such as central porosity and shrinkage cavities in the billet, significantly increasing the equiaxed crystal ratio and laying a solid foundation for producing high-quality steel.

[0053] In summary, this invention, through composition optimization and process control, reduces the occurrence of defects such as central porosity and intermediate cracks in the billet, significantly improves the strength, toughness, and resistance to hydrogen sulfide stress corrosion of the steel, provides a reliable guarantee for the production of high-end oil casing steel, effectively meets the urgent demand of the oil and gas extraction industry for high-performance steel, and has high application value. Attached Figure Description

[0054] Figure 1 This is a low-magnification photograph of the continuously cast billet prepared in Example 1 of the present invention;

[0055] Figure 2 The image shows the metallographic structure of the 110ksi steel-grade anti-sulfur product prepared in Example 1 of this invention.

[0056] Figure 3 The image shows the metallographic structure of the 110ksi steel-grade anti-sulfur product prepared in Comparative Example 1 of this invention.

[0057] Figure 4 This is a photograph of the morphology of the inclusions prepared in Comparative Example 3 of the present invention. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0059] To better illustrate the present invention, further examples are provided below.

[0060] The mass percentage of calcium carbon spheres used in the following examples is as follows: CaO 65%~70%, C 25%~30%, Al2O3 3%~5%, H2O≤1.5%, with the balance being unavoidable impurity elements.

[0061] Of the scrap steel used: 46% to 50% is scrap steel with a thickness of ≥4mm, 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. The length and width of the scrap steel are ≤800mm.

[0062] The thickness of the pressed blocks is 0.8mm~1.2mm, and the length, width, and height of the pressed blocks are all ≤1000mm. The chemical composition and mass percentage of the pressed blocks are: C 0.06%~0.50%, Si 0.15%~0.35%, Mn 0.2%~1.8%, Cr 0.06%~3%, with the balance being other elements.

[0063] The chemical composition and mass percentage of the pre-deoxidizer used are as follows: Al 22%~25%, Al2O3 20%~22%, CaO 25%~27%, Si 8%~9%, with the balance being other elements.

[0064] The synthetic slag used includes the following components by mass percentage: Al2O3 45%~50%, CaO 32%~40%, SiO2 4%~10%, MgO <3%, with the balance being other elements.

[0065] The aluminum sheets used contain ≥98% Al. The aluminum ingots contain ≥99% Al.

[0066] The electric furnace operates in constant power mode throughout the power supply process. The output power is based on the transformer's rated power overload of 15-20%. The voltage is 812V and the current is 50520±50A. The voltage is 864V and the current is 47480±50A. The voltage is 890V and the current is 46090±50A.

[0067] Example 1

[0068] This invention provides a 110ksi grade steel for oil casing, the chemical composition and mass percentage of which are as follows:

[0069] C 0.20%, Si 0.26%, Mn 0.55%, P 0.007%, S 0.0011%, Al 0.025%, Cr 0.55%, Mo 0.72%, V 0.13%, Ti 0.015%, B 0.0015%; Sn+As+Pb+Bi+Sb≤0.012%, and the content of each element ≤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.

[0070] The production process of the aforementioned 110ksi grade steel for oil casing includes the following steps:

[0071] S1, Scrap Steel Loading: The total loading volume of steel material is 90t, divided into three loading stages: the first loading volume is 40t, including 28t of scrap steel, 10t of briquettes, and 2t of calcium carbon balls; the second loading volume is 30t, including 21t of scrap steel, 7.5t of briquettes, and 1.5t of calcium carbon balls; the third loading volume is 20t, including 17t of scrap steel, 2.4t of briquettes, and 0.6t of calcium carbon balls; during each loading, 50% of the total calcium carbon balls are placed at a height of 1 / 8h, 30% are placed at a height of 1 / 4h, and the remainder are placed at a height of 1 / 2h; h is the height of the highest material level from the bottom of the tank during each loading stage;

[0072] S2, Electric Furnace Smelting: After the initial charge is introduced, power is supplied at level 5 for the first 2 minutes, level 3 for 2-5 minutes, and level 2 after 5 minutes, while maintaining an oxygen supply intensity of 0.42 Nm. 3 / min·t, when the primary charge has melted to 82%, power is cut off and secondary charge is added. After the secondary charge is added, power is supplied at level 5 for the first 2 minutes, level 3 for 2-4 minutes, and level 2 after 4 minutes, while maintaining an oxygen supply intensity of 0.42 Nm. 3 / min·t, when the secondary charge has melted 87%, power is cut off to add the tertiary charge. After the tertiary charge is added, power is supplied at level 5 for the first 2 minutes, level 3 for 2-4 minutes, and level 2 after 4 minutes, while maintaining an oxygen supply intensity of 0.43 Nm. 3 / min·t, after smelting for 10 minutes, maintain an oxygen supply intensity of 0.62 Nm. 3 When the steel temperature is 1580℃, the steel is sampled and tapped when the P content in the electric furnace molten steel is 0.0046% and the C content is 0.064%. At this time, the w(FeO) in the slag is 17%, the basicity CaO / SiO2 is 2.6, and the w(CaO) / w(FeO) is 2.2.

[0073] S3, electric arc furnace tapping, total electric arc furnace tapping volume 85t / heat. When the electric arc furnace tapping volume reaches 10% of the total, pre-deoxidizer is added. When the electric arc furnace tapping volume reaches 15% of the total, 2.0kg / t aluminum ingot is added. When the electric arc furnace tapping volume reaches 25% of the total, silicon-manganese alloy, high-carbon ferrochrome, ferromolybdenum and vanadium-nitrogen alloy are added in sequence. When the electric arc furnace tapping volume reaches 35%, 6kg / t lime, 3.5kg / t synthetic slag, 3.3kg / t fluorite and 0.5kg / t aluminum sheet are added.

[0074] S4, Refining and Slag Forming: 1 minute after power supply, add 0.7 kg / t of calcium carbide and 0.5 kg / t of aluminum granules. 12 minutes after power supply, the temperature of the molten steel reaches 1590℃. Take samples for testing and adjust the alloy composition to meet the design requirements. Based on the results of the refining slag sample, adjust the refining slag composition to meet the following requirements: 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.

[0075] S5, VD Vacuum Refining: Remove 66% of the refining slag, then perform 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 at 180NL / min for 15min, then reduce the argon blowing rate to 100NL / min and maintain it for 4min, then break the vacuum, control the argon blowing rate at 8NL / min, 5min after breaking the vacuum, add 0.35kg / t ferrotitanium, break the vacuum for 10min, add 0.028kg / t ferroboron, break the vacuum for 20min, and proceed to the next process. The ferroboron recovery rate is 78%.

[0076] S6, Continuous Casting Process: The continuous casting process employs secondary cooling combined with electromagnetic stirring in the crystallizer and final electromagnetic stirring. The primary cooling water flow rate is 1.22 m³ / h. 3 / t, the secondary cooling water flow rate is 0.33m³ / t. 3 / t, the electromagnetic stirring current of the crystallizer is 380A, the frequency is 4Hz, the electromagnetic stirring current at the end is 370A, the frequency is 8Hz, the superheat is 23℃, and the pulling speed is 2.0m / min.

[0077] The continuously cast billets prepared in this embodiment were tested according to YB / T 4149-2018, "Inspection and Judgment Method for Continuously Cast Round Tube Billets". The test results for central porosity, shrinkage cavities, central cracks, intermediate cracks, subcutaneous cracks, subcutaneous bubbles, and equiaxed crystals are shown in Table 1. Figure 1 As shown.

[0078] Table 1

[0079]

[0080] Note: Traditional steelmaking process refers to the EAF-LF-VD-CC process flow. In the electric arc furnace (EAF) smelting process, all steel materials are used, including 76-80% scrap steel, 20-22% briquettes, 1-1.5% carbon in microcrystalline blocks, and lime for slag formation at a rate of 23-30 kg / t steel. The remaining operations are the same as in Example 1. During the EAF tapping process, no pre-deoxidizer is used for pre-deoxidation, and no aluminum sheets are used for slag surface deoxidation. The timing of the addition of specific materials is not controlled. The remaining operations are the same as in Example 1. In the refining process, the slag composition is specified as follows: CaO 50-55%, SiO2 7-9%, Al2O3 20-27%, MgO 4-6%, FeO+MnO < 1%, w(CaO) / w(SiO2) = 6.0-7.0. The remaining operating steps are the same as in Example 1. In the VD smelting process, slag removal is not performed, and the argon flow rate throughout the VD process is constant at 70 NL / min. The remaining operations are the same as in Example 1. The flow rate of the cooling water in the continuous casting process is 1.4 m³ / s. 3 / t~1.6m 3 / t, the secondary cooling water flow rate is 0.35m³ / t. 3 / t~0.37m 3 / t, the superheat is 20℃~30℃, and the remaining operation steps are the same as in Example 1.

[0081] Following conventional ring furnace heating, piercing, rolling, micro-tension diameter reduction, straightening, finishing, quenching, and tempering, a 110ksi grade sulfur-resistant product was obtained, and its metallographic structure is shown in the figure below. Figure 2 As shown, the grain size of the microstructure is grade 11.0.

[0082] The rolled products were sampled and tested in accordance with GB / T 10561-2023, as shown in Table 2.

[0083] Table 2

[0084]

[0085] Example 2

[0086] This invention provides a 110ksi grade steel for oil casing, the chemical composition and mass percentage of which are as follows:

[0087] C 0.18%, Si 0.25%, Mn 0.50%, P 0.008%, S 0.0013%, Al 0.010%, Cr 0.50%, Mo 0.70%, V 0.15%, Ti 0.01%, B 0.0020%; Sn+As+Pb+Bi+Sb≤0.016%, and the content of each element ≤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.

[0088] The production process of the aforementioned 110ksi grade steel for oil casing includes the following steps:

[0089] S1, Scrap Steel Loading: The total loading volume of steel material is 90t, divided into three loading stages: the first loading volume is 40t, including 28t of scrap steel, 10t of briquettes, and 2t of calcium carbon balls; the second loading volume is 30t, including 21t of scrap steel, 7.5t of briquettes, and 1.5t of calcium carbon balls; the third loading volume is 20t, including 17t of scrap steel, 2.4t of briquettes, and 0.6t of calcium carbon balls; during each loading, 50% of the total calcium carbon balls are placed at a height of 1 / 8h, 30% are placed at a height of 1 / 4h, and the remainder are placed at a height of 1 / 2h; h is the height of the highest material level from the bottom of the tank during each loading stage;

[0090] S2, Electric Furnace Smelting: After the initial charge is introduced, power is supplied at level 5 for the first 2 minutes, level 3 for 2-5 minutes, and level 2 after 5 minutes, while maintaining an oxygen supply intensity of 0.5 Nm. 3 / min·t, when the primary charge has melted to 80%, power is cut off and secondary charge is added. After the secondary charge is added, power is supplied at level 5 for the first 2 minutes, level 3 for 2-4 minutes, and level 2 after 4 minutes, while maintaining an oxygen supply intensity of 0.51 Nm. 3 / min·t, when the secondary charge has melted 85%, power is cut off to add the tertiary charge. After the tertiary charge is added, power is supplied at level 5 for the first 2 minutes, level 3 for 2-4 minutes, and level 2 after 4 minutes, while maintaining an oxygen supply intensity of 0.52 Nm. 3 / min·t, maintaining an oxygen supply intensity of 0.71 Nm after smelting for 11 minutes. 3 When the steel temperature is 1580℃, the steel is sampled and tapped when the P content in the electric furnace molten steel is 0.0047% and the C content is 0.063%. At this time, the w(FeO) in the slag is 16%, the basicity CaO / SiO2 is 2.6, and the w(CaO) / w(FeO) is 2.6.

[0091] S3, electric arc furnace tapping, total electric arc furnace tapping volume 84t / heat. When the electric arc furnace tapping volume reaches 9% of the total, pre-deoxidizer is added. When the electric arc furnace tapping volume reaches 14% of the total, 1.9kg / t aluminum ingot is added. When the electric arc furnace tapping volume reaches 24% of the total, silicon-manganese alloy, high-carbon ferrochrome, ferromolybdenum and vanadium-nitrogen alloy are added in sequence. When the electric arc furnace tapping volume reaches 34%, 5.5kg / t lime, 3.2kg / t synthetic slag, 3.4kg / t fluorite and 0.4kg / t aluminum sheet are added.

[0092] S4, Refining and Slag Forming: 1 minute after power supply, add 0.6 kg / t of calcium carbide and 0.4 kg / t of aluminum granules. 11 minutes after power supply, the temperature of the molten steel reaches 1600℃. Take samples for testing and adjust the alloy composition to meet the design requirements. Based on the results of the refining slag sample, adjust the refining slag composition to meet the following requirements: 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.

[0093] S5, VD Vacuum Refining: Remove 60% of the refining slag, then perform 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 at 160NL / min for 17min, then reduce the argon blowing rate to 110NL / min and maintain it for 3min, then break the vacuum, control the argon blowing rate at 5NL / min, 6min after breaking the vacuum, add 0.3kg / t ferrotitanium, 11min after breaking the vacuum, add 0.023kg / t ferroboron, 21min after breaking the vacuum, and proceed to the next process. The ferroboron yield is 77%.

[0094] S6, Continuous Casting Process: The continuous casting process employs secondary cooling combined with electromagnetic stirring in the crystallizer and end-stage electromagnetic stirring. The primary cooling water flow rate is 1.3 m³ / h. 3 / t, the secondary cooling water flow rate is 0.32m³ / t. 3 / t, the electromagnetic stirring current of the crystallizer is 360A, the frequency is 3Hz, the electromagnetic stirring current at the end is 370A, the frequency is 7Hz, the superheat is 20℃, and the pulling speed is 1.3m / min.

[0095] Example 3

[0096] This invention provides a 110ksi grade steel for oil casing, the chemical composition and mass percentage of which are as follows:

[0097] C 0.22%, Si 0.35%, Mn 0.60%, P 0.007%, S 0.0014%, Al 0.04%, Cr 0.60%, Mo 0.75%, 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.

[0098] The production process of the aforementioned 110ksi grade steel for oil casing includes the following steps:

[0099] S1, Scrap Steel Loading: The total loading volume of steel material is 90t, divided into three loading stages: the first loading volume is 40t, including 28t of scrap steel, 10t of briquettes, and 2t of calcium carbon balls; the second loading volume is 30t, including 21t of scrap steel, 7.5t of briquettes, and 1.5t of calcium carbon balls; the third loading volume is 20t, including 17t of scrap steel, 2.4t of briquettes, and 0.6t of calcium carbon balls; during each loading, 50% of the total calcium carbon balls are placed at a height of 1 / 8h, 30% are placed at a height of 1 / 4h, and the remainder are placed at a height of 1 / 2h; h is the height of the highest material level from the bottom of the tank during each loading stage;

[0100] S2, Electric Furnace Smelting: After the initial charge is introduced, power is supplied at level 5 for the first 2 minutes, level 3 for 2-5 minutes, and level 2 after 5 minutes, while maintaining an oxygen supply intensity of 0.58 Nm. 3 / min·t, when the primary charge has melted to 85%, power is cut off and secondary charge is added. After the secondary charge is added, power is supplied at level 5 for the first 2 minutes, level 3 for 2-4 minutes, and level 2 after 4 minutes, while maintaining an oxygen supply intensity of 0.57 Nm. 3 / min·t, when the secondary charge has melted 90%, power is cut off to add the tertiary charge. After the tertiary charge is added, power is supplied at level 5 for the first 2 minutes, level 3 for 2-4 minutes, and level 2 after 4 minutes, while maintaining an oxygen supply intensity of 0.58 Nm. 3 / min·t, maintaining an oxygen supply intensity of 0.78 Nm after smelting for 12 minutes. 3 When the steel temperature is 1580℃, the steel is sampled and tapped when the P content in the electric furnace molten steel is 0.0048% and the C content is 0.061%. At this time, the w(FeO) in the slag is 19%, the basicity CaO / SiO2 is 2.7, and the w(CaO) / w(FeO) is 3.1.

[0101] S3, electric arc furnace tapping, total electric arc furnace tapping volume 87t / heat. When the electric arc furnace tapping volume reaches 11% of the total, pre-deoxidizer is added. When the electric arc furnace tapping volume reaches 16% of the total, 2.1kg / t aluminum ingot is added. When the electric arc furnace tapping volume reaches 26% of the total, silicon-manganese alloy, high-carbon ferrochrome, ferromolybdenum and vanadium-nitrogen alloy are added in sequence. When the electric arc furnace tapping volume reaches 36%, 6.5kg / t lime, 3.4kg / t synthetic slag, 3.6kg / t fluorite and 0.6kg / t aluminum sheet are added.

[0102] S4, Refining and Slag Forming: 2 minutes after power supply, add 0.8 kg / t of calcium carbide and 0.6 kg / t of aluminum granules. 10 minutes after power supply, the temperature of the molten steel reaches 1590℃. Take samples for testing and adjust the alloy composition to meet the design requirements. Based on the results of the refining slag sample, adjust the refining slag composition to meet the following requirements: 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.

[0103] S5, VD Vacuum Refining: Remove 70% of the refining slag, then perform 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 and maintain it for 5min, then break the vacuum, control the argon blowing rate at 10NL / min, 7min after breaking the vacuum, add 0.4kg / t ferrotitanium, break the vacuum for 10min~12min, add 0.04kg / t ferroboron, 22min after breaking the vacuum, proceed to the next process, ferroboron yield is 78%;

[0104] S6, Continuous Casting Process: The continuous casting process employs secondary cooling combined with electromagnetic stirring in the crystallizer and end-stage electromagnetic stirring. The primary cooling water flow rate is 1.4 m³ / h. 3 / t, the secondary cooling water flow rate is 0.34m³ / t. 3 / t, the electromagnetic stirring current of the crystallizer is 400A, the frequency is 5Hz, the electromagnetic stirring current at the end is 390A, the frequency is 9Hz, the superheat is 25℃, and the pulling speed is 2.1m / min.

[0105] The highest inclusion grade of the 110ksi steel-grade anti-sulfur products prepared in Examples 2 and 3 was 0.5.

[0106] The mechanical properties of the 110ksi grade anti-sulfur products prepared according to ISO 6892-1:2019 standard were tested against those of the 110ksi grade anti-sulfur products prepared in Examples 1-3, and SSC testing was performed according to NACE TM0177-2016 standard. The yield strength of the products was 850-860 MPa, the tensile strength was 880-900 MPa, the elongation was 27%-30%, and the longitudinal full-size impact energy (0℃) was 220-225 J. The products exhibited excellent resistance to hydrogen sulfide stress corrosion, with a 98% pass rate for SSC A method (A liquid) without fracture after 720 hours and a 96% pass rate after 1000 hours.

[0107] Comparative Example 1

[0108] This comparative example provides a 110ksi grade steel for oil casing, which differs from Example 1 only in that its chemical composition does not contain element B, that is, ferroboron is not added during the VD vacuum refining process.

[0109] Following conventional ring furnace heating, piercing, rolling, micro-tension diameter reduction, straightening, finishing, quenching, and tempering, a 110ksi grade sulfur-resistant product was obtained, and its metallographic structure is shown in the figure below. Figure 3 As shown, the grain size of the microstructure is grade 8.5.

[0110] The continuously cast billets prepared in this comparative example were tested according to the YB / T 4149-2018 method for testing and judging continuously cast round tube billets. The test results of central porosity, shrinkage cavities, central cracks, intermediate cracks, subcutaneous cracks, subcutaneous bubbles and equiaxed crystals of the continuously cast billets are shown in Table 3.

[0111] Table 3

[0112]

[0113] The inclusions are shown in Table 4.

[0114] Table 4

[0115]

[0116] 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 non-fracture pass rate of 94% when kept in liquid A for 720 hours using the SSC A method. However, the yield strength does not meet the requirements (the minimum standard is 750 MPa).

[0117] Comparative Example 2

[0118] This comparative example provides a 110ksi grade steel for oil casing, differing from Example 1 only in that graphite spheres are used instead of calcium carbon spheres in the scrap steel feedstock, and lime is added during the electric furnace smelting process for slag formation. The specific steps are as follows:

[0119] S1, Scrap Steel Loading: The total loading amount of steel material is 90t, which is divided into three loading stages: the first loading amount is 40t, of which 29.5t is scrap steel, 10t is briquettes, and 0.5t is graphite balls; the second loading amount is 30t, of which 22t is scrap steel, 7.5t is briquettes, and 0.5t is graphite balls; the third loading amount is 20t, of which 17t is scrap steel and 3t is briquettes.

[0120] S2, after the initial material loading, add 45 kg / t of lime into the furnace 5 minutes after power is supplied, while maintaining an oxygen supply intensity of 0.42 Nm. 3 When the primary charge melts to 80%, power is cut off and secondary charge is added. After the secondary charge is added, power is restored and smelting continues for 4 minutes. Lime is added to the furnace at a rate of 15 kg / t, while maintaining an oxygen supply intensity of 0.42 Nm³ / min·t. When the secondary charge melts to 87%, power is cut off and tertiary charge is added, maintaining an oxygen supply intensity of 0.43 Nm³ / min·t. 3 / min·t, after smelting for 10 minutes, maintain an oxygen supply intensity of 0.62 Nm. 3 The sample was taken at a temperature of 1580℃ and the P content in the molten steel was 0.016% per min·t, which did not meet the requirement of reducing the P content to below 0.005%.

[0121] S3~S6: Same as Example 1.

[0122] The impact performance of the product obtained after the above-prepared continuous casting billet was tested according to the conventional ring furnace heating, piercing, rolling, micro-tension reduction, straightening, finishing, quenching and tempering. The longitudinal full-size impact energy (0℃) was 88J (the standard requires more than 100J).

[0123] Comparative Example 3

[0124] This comparative example provides a 110ksi grade steel for oil casing, differing from Example 1 only in that the addition of aluminum sheets is omitted when the electric furnace tapping reaches 34% of the steel content; otherwise, the steps are identical.

[0125] S1~S2, same as in Example 1;

[0126] S3, Electric Furnace Steelmaking: The total steelmaking volume of the electric furnace is 84t / furnace. When the steelmaking volume reaches 9% of the total, a pre-deoxidizer is added. When the steelmaking volume reaches 14% of the total, 1.9kg / t aluminum ingot is added. When the steelmaking volume reaches 24% of the total, silicon-manganese alloy, high-carbon ferrochrome, ferromolybdenum and vanadium-nitrogen alloy are added in sequence. When the steelmaking volume reaches 34% of the total, 5.5kg / t lime, 3.2kg / t synthetic slag and 3.4kg / t fluorite are added.

[0127] S4~S6: Same as Example 1.

[0128] The FeO+MnO content in the refining slag after S4 refining and slagging is 1.2%, and the inclusion content is relatively high after rolling, such as... Figure 4 As shown.

[0129] The highest level of inclusions was 2.5, which affected the SCC pass rate. Ultimately, the SCC sample broke after only 96 hours in the hanging test.

[0130] 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 within the protection scope of the present invention.

Claims

1. A high-strength, high-toughness, corrosion-resistant steel, characterized in that, Its chemical composition and mass percentage are as follows: 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, toughness and corrosion-resistant steel includes electric furnace smelting, electric furnace tapping, refining and slag making, VD vacuum refining and continuous casting. The steelmaking raw materials for the electric furnace smelting process include scrap steel, calcium carbon balls, and briquettes; the C content in the molten steel after smelting is controlled to be 0.06%~0.09%, the P content to be ≤0.005%, and the w(FeO) in the slag to be 15%~20%, the basicity CaO / SiO2 to be 2.5~3.0, and the w(CaO) / w(FeO) to be 2.0~3.

5. The specific material distribution method in the electric furnace smelting process is as follows: The steelmaking raw materials are distributed in three stages; the first distribution accounts for 44% to 46% of the total steelmaking raw materials, the second distribution accounts for 32% to 34% of the total steelmaking raw materials, and the third distribution accounts for 21% to 23% of the total steelmaking raw materials. In the primary and secondary feeding processes, scrap steel accounts for 69% to 71%, calcium carbon balls account for 4% to 6%, and briquettes account for 24% to 26%. In the tertiary feeding process, scrap steel accounts for 84% to 86%, calcium carbon balls account for 2% to 4%, and briquettes account for 11% to 13%. In each feeding operation, 49% to 51% of the total amount of calcium carbon balls are placed at a height of 0.12h to 0.13h, 29% to 31% are placed at a height of 0.24h to 0.26h, and the remainder is placed at a height of 0.48h to 0.52h; h is the height of the highest material level from the bottom of the tank in each feeding operation. The electric arc furnace tapping process includes: when the electric arc furnace taps steel to 9%~11% of the total amount, adding a pre-deoxidizer; when the electric arc furnace taps steel to 14%~16% of the total amount, adding aluminum ingots; when the electric arc furnace taps steel to 24%~26% of the total amount, sequentially adding silicon-manganese alloy, high-carbon ferrochrome, ferromolybdenum and vanadium-nitrogen alloy; and when the electric arc furnace taps steel to 34%~36% of the total amount, adding lime, synthetic slag, fluorite and aluminum flakes. In the refining slag-making process, the refining slag includes the following components by mass percentage: 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, This includes the electric furnace smelting process, the electric furnace tapping process, the refining and slag-making process, the VD vacuum refining process, and the continuous casting process; The steelmaking raw materials for the electric furnace smelting process include scrap steel, calcium carbon balls, and briquettes; the C content in the molten steel after smelting is controlled to be 0.06%~0.09%, the P content to be ≤0.005%, and the w(FeO) in the slag to be 15%~20%, the basicity CaO / SiO2 to be 2.5~3.0, and the w(CaO) / w(FeO) to be 2.0~3.

5. The electric arc furnace tapping process includes: when the electric arc furnace taps steel to 9%~11% of the total amount, adding a pre-deoxidizer; when the electric arc furnace taps steel to 14%~16% of the total amount, adding aluminum ingots; when the electric arc furnace taps steel to 24%~26% of the total amount, sequentially adding silicon-manganese alloy, high-carbon ferrochrome, ferromolybdenum and vanadium-nitrogen alloy; and when the electric arc furnace taps steel to 34%~36% of the total amount, adding lime, synthetic slag, fluorite and aluminum flakes. In the refining slag-making process, the refining slag includes the following components by mass percentage: 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, toughness, and corrosion-resistant steel as described in claim 2, characterized in that, The specific material distribution method in the electric furnace smelting process is as follows: The steelmaking raw materials are distributed in three stages; the first distribution accounts for 44% to 46% of the total steelmaking raw materials, the second distribution accounts for 32% to 34% of the total steelmaking raw materials, and the third distribution accounts for 21% to 23% of the total steelmaking raw materials. In the primary and secondary feeding processes, scrap steel accounts for 69% to 71%, calcium carbon balls account for 4% to 6%, and briquettes account for 24% to 26%. In the tertiary feeding process, scrap steel accounts for 84% to 86%, calcium carbon balls account for 2% to 4%, and briquettes account for 11% to 13%. In each feeding operation, 49% to 51% of the total amount of calcium carbon balls are placed at a height of 0.12h to 0.13h, 29% to 31% are placed at a height of 0.24h to 0.26h, and the remainder is placed at a height of 0.48h to 0.52h; h is the height of the highest material level of each feeding operation from the bottom of the tank.

4. The production process of high-strength, toughness, and corrosion-resistant steel as described in 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%, with the balance being unavoidable impurity elements; and / or By mass percentage, the scrap steel comprises: 46%~50% scrap steel with a thickness ≥ 4mm, 48%~52% scrap steel with a thickness of 2mm~4mm, and the remainder being scrap steel with a thickness of less than 2mm; and / or The thickness of the pressing block is 0.8mm to 1.2mm.

5. The production process of high-strength, toughness, and corrosion-resistant steel as described in claim 3, characterized in that, The specific steps of the electric furnace smelting process include: After the fabric is laid, it is smelted by electricity, maintaining an oxygen supply intensity of 0.4 Nm. 3 / min·t~0.6Nm 3 / min·t, when the primary charge has melted 80%~85%, power is cut off for secondary charging, then power is restored for smelting, maintaining an oxygen supply intensity of 0.4Nm. 3 / min·t~0.6Nm 3 / min·t, when the secondary furnace charge has melted 85%~90%, power is cut off for a third charging operation, followed by power restoration for smelting, while maintaining an oxygen supply intensity of 0.4Nm. 3 / min·t~0.6Nm 3 / min·t, after smelting for 10-12 minutes, maintain an oxygen supply intensity of 0.6 Nm. 3 / min·t~0.8Nm 3 / min·t, until steel is tapped.

6. The production process of high-strength, toughness, and corrosion-resistant steel as described in claim 5, characterized in that, After one fabric application, within 2 minutes of power supply, the supply voltage is 812V and the current is 50470A~50570A; from 2 minutes to 5 minutes of power supply, the supply voltage is 864V and the current is 47430A~47530A; after 5 minutes of power supply, the supply voltage is 890V and the current is 46040A~460140A. After the second fabric application, within 2 minutes of power supply, the supply voltage is 812V and the current is 50470A~50570A; from 2 minutes to 4 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. After three fabric applications, within 2 minutes of power supply, the supply voltage was 812V and the current was 50470A~50570A; from 2 minutes to 4 minutes of power supply, the supply voltage was 864V and the current was 47430A~47530A; after 4 minutes of power supply, the supply voltage was 890V and the current was 46040A~460140A.

7. The production process of high-strength, toughness, and corrosion-resistant steel as described in claim 2, characterized in that, In the electric arc 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%, with the balance being other elements; and / or The synthetic slag comprises the following components by mass percentage: Al2O3 45%~50%, CaO 32%~40%, SiO2 4%~10%, MgO <3%, with the balance being other elements.

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

9. The production process of high-strength, toughness, and corrosion-resistant steel as described in claim 2, characterized in that, The VD vacuum refining process specifically includes the following steps: Remove 60%~70% of the refining slag, then perform VD vacuum refining. When the vacuum degree is 10kPa~100kPa, the argon blowing rate is 40NL / min~60NL / min; when the vacuum degree is 5kPa~10kPa, the argon blowing rate is 60NL / min~100NL / min; when the vacuum degree is 500Pa~5kPa, the argon blowing rate is 100NL / min~140NL / min; when the vacuum degree is 67Pa~500Pa, the argon blowing rate is 140NL / min~160NL / min. 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 and maintain it for 3min~5min, then break the vacuum, control the argon blowing rate at 5NL / min~10NL / min, add ferrotitanium 5min~7min after breaking the vacuum, add ferroboron 10min~12min after breaking the vacuum, and proceed to the next process 20min~22min after breaking the vacuum.

10. The production process of high-strength, toughness, and corrosion-resistant steel as described in claim 2, characterized in that, In the continuous casting process, the flow rate of the first cooling water is 1.2 m³ / h. 3 / t~1.4m 3 / t, the secondary cooling water flow rate is 0.32m³ / t. 3 / t~0.34m 3 / t, the electromagnetic stirring current of the crystallizer is 350A~400A, the frequency is 3Hz~5Hz, the electromagnetic stirring current at the end 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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