High-strength and high-toughness low-temperature marine steel plate with good strain aging performance and manufacturing method thereof

Abstract

The application discloses a high-strength and high-toughness low-temperature marine steel plate with good strain aging performance and a manufacturing method thereof, and belongs to the technical field of steel material preparation.The chemical composition of the high-strength and high-toughness low-temperature marine steel plate is as follows in percentage by weight: C: 0.02%-0.05%, Si: 0.15%-0.45%, Mn: 1.6%-2.3%, Nb: 0.04%-0.08%, Ti: 0.006%-0.02%, Cu: 0.20%-0.55%, Ni: 0.3%-0.8%, Zr: 0.3%-0.7%, B: 0.001%-0.0025%, Al: 0.035%-0.075%, Hf: 0.005%-0.025%, Y: 0.015%-0.035%, S: ≤0.0015%, P: ≤0.008%, and the rest is iron and inevitable impurities.The yield strength of the marine steel plate is greater than or equal to 460 Mpa, the tensile strength is 590-700 Mpa, the elongation is greater than or equal to 20%, and the impact energy at-60 DEG C after strain aging is greater than or equal to 200 J, so that the problem that the safety use of marine equipment under the extremely low temperature and harsh conditions in the polar region cannot be guaranteed is solved.

Description

Technical Field

[0001] This invention belongs to the field of steel material preparation technology, specifically a high-strength, high-toughness, low-temperature marine steel plate with good strain aging properties and its manufacturing method. Background Technology

[0002] With the proposal of the modern energy system plan, "increasing oil and gas exploration and development, adhering to both conventional and non-conventional approaches, and giving equal importance to onshore and offshore operations" and "consolidating and expanding overseas energy resource security capabilities and improving cooperation in major overseas oil and gas producing areas" have become the top priorities for the development of the oil and gas industry and the guarantee of national energy security.

[0003] The polar regions have harsh natural environments, presenting challenges such as low temperatures, sea ice obstruction, iceberg attacks, and blizzards. Therefore, steel plates used in polar marine engineering must possess excellent strength-toughness matching and strain-aging properties under low-temperature conditions to ensure personnel safety and extend the service life of engineering equipment after cold working processes such as cold straightening, bending, and edge bending.

[0004] Patent CN102828114A, entitled "A Steel Plate for Marine Engineering with Excellent Strain Aging Properties and Its Manufacturing Method," provides a steel plate for marine engineering with excellent strain aging properties and its manufacturing method. It employs a controlled rolling and cooling process, followed by quenching and tempering, resulting in a marine engineering steel plate with high strength, high plasticity, good Z-axis resistance to lamellar tearing, and excellent strain aging properties. However, it uses a TMCP+RQT process, which is relatively complex, energy-intensive, increases costs, and prolongs the production cycle.

[0005] The patent CN110760765B, entitled "Ultra-low cost, high elongation and strain aging embrittlement 600MPa grade tempered steel plate and its manufacturing method," discloses a method based on an ultra-low C-Mn-(Ti+Nb+V+B) microalloyed steel composition system. This method controls Mn / C ≥ 22, (Ni+Mo+Cr) alloying, and (%B) - 0.714{(%N) - [0.292(%Ti) + 0.518(%Al)×ξ]} ≥ 6×10-4. It also optimizes the rolling process and quenching at 12300 ≤ [1 / 4(Ac1) + 3 / 4(Ac3)] × (t quenching) ≤ 15900, followed by tempering at 550–600℃. This results in a finished steel plate with a microstructure of fine, uniform equiaxed ferrite grains + low-carbon lower bainite, with an average grain size below 15μm. However, the steel plate was only evaluated for its impact toughness at -40℃ and its strain-aged impact performance at -20℃, which is far from meeting the requirements for use in polar environments.

[0006] Patent CN103031498B, entitled "Manufacturing Method of Low-Compression Thickness Ultra-High Strength Strain-Aged Marine Engineering Steel Plate," provides a method for manufacturing low-compression thickness ultra-high strength strain-aged marine engineering steel plates. The method involves converter smelting, LF and RH refining, and the rational setting and optimization of controlled rolling and cooling processes, followed by tempering heat treatment. The invented steel plate exhibits good performance, with a tensile strength of 780–850 MPa, a yield strength of 720–800 MPa, an elongation of 18–21%, a transverse impact strength of ≥120 J at -40℃, and an aging impact strength of ≥100 J at -40℃. It possesses ultra-high strength, high toughness, and excellent low-temperature aging toughness, and the production process is stable. However, it only evaluates the strain-aged impact performance at -40℃, and the impact energy is relatively low, which cannot meet the requirements for use in harsh, low-temperature polar environments.

[0007] Therefore, it is urgent to research and develop high-strength, high-toughness, low-temperature marine engineering steel plates with good strain aging properties for new polar marine engineering equipment. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a high-strength, high-toughness, low-temperature marine engineering steel plate with excellent strain aging properties and its manufacturing method. This invention utilizes a low-precious metal alloy content design, employing the composite addition of elements such as hafnium, zirconium, and yttrium. Through a coupled alloy composition design, smelting, and controlled rolling / cooling process, a marine engineering steel plate with a thickness of 60mm-80mm is produced. This plate exhibits high strength and toughness (yield strength ≥460MPa, tensile strength 590-700MPa, elongation ≥20%) under low-temperature conditions and excellent strain aging properties (impact energy ≥200J at -60℃). This solves the problem of unreliable safe operation of marine engineering equipment under harsh polar and low-temperature conditions.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] This invention provides a high-strength, high-toughness, low-temperature marine engineering steel plate with excellent strain aging properties. The chemical composition and weight percentage of the high-strength, high-toughness, low-temperature marine engineering steel plate are as follows: C: 0.02%-0.05%, Si: 0.15%-0.45%, Mn: 1.6%-2.3%, Nb: 0.04%-0.08%, Ti: 0.006%-0.02%, Cu: 0.20%-0.55%, Ni: 0.3%-0.8%, Zr: 0.3%-0.7%, B: 0.001%-0.0025%, Al: 0.035%-0.075%, Hf: 0.005%-0.025%, Y: 0.015%-0.035%, S: ≤0.0015%, P ≤0.008%, with the remainder being iron and unavoidable impurities.

[0011] The mechanism of action of each alloy component in the high-strength, high-toughness, low-temperature marine engineering steel plate of this invention is as follows:

[0012] C: C has a significant impact on the strength, hardenability, low-temperature toughness, and aging sensitivity of steel. If the C content is too high, the low-temperature toughness of the steel will decrease sharply. At the same time, C in the solid solution state after deformation will agglomerate at dislocations, pinning dislocations and hindering their movement, thereby reducing the low-temperature aging toughness of the steel. If the C content is too low, the steel plate cannot be guaranteed to have sufficient strength. The present invention controls the C content within the range of 0.02%-0.05%.

[0013] Si (Si): Excessive O (O) and S (S) content in molten steel during steelmaking hinders the removal of N (N), thus increasing the steel's aging sensitivity. As a reducing agent and deoxidizer, adding a certain amount of Si can effectively remove O from steel. Simultaneously, Si dissolves in austenite and ferrite, improving the steel's strength and hardenability. However, excessive Si content leads to the formation of large amounts of blocky ferrite, significantly reducing the steel's low-temperature toughness and ductility. This invention controls the Si content within the range of 0.15%-0.45%.

[0014] Mn: Mn is a good desulfurizer and deoxidizer, reducing the adverse effects of elements such as O and S on steel. Adding a certain amount of manganese can lower the brittle transition temperature of steel, improve hardenability and strength, and is beneficial to the low-temperature toughness of steel. However, excessive manganese content will slow down the diffusion rate of C in steel and hinder the formation of carbides. In this invention, the Mn content is controlled within the range of 1.6%-2.3%.

[0015] Nb: In steel, Nb combines with C and N to form highly dispersed carbonitride compounds, pinning austenite grain boundaries and hindering austenite grain growth, thus refining the austenite grains. Deformation in the austenite region causes strain-induced precipitation of the dispersed carbonitrides, delaying recrystallization and improving the strength and low-temperature toughness of the steel plate. In the high-temperature ferrite region, it forms very fine semi-coherent particles, resulting in significant precipitation hardening. Simultaneously, it removes free C and N elements from the steel, improving the low-temperature aging properties of the steel plate. This invention controls the Nb content to be within the range of 0.04%-0.08%.

[0016] Ti: Ti is a strong ferrite-forming element with a strong affinity for O, C, and N, effectively deoxidizing and fixing nitrogen and carbon. The resulting TiC exhibits extremely high stability and precipitates in large quantities at low temperatures, inhibiting grain growth and coarsening in steel. During cooling, the eutectic reaction leads to the dispersed precipitation of TiFe2, resulting in precipitation hardening. Simultaneously, Ti has a strong affinity for S, forming hard sulfides, thus resolving the anisotropy of low-temperature toughness in steel plates caused by elongated manganese sulfides. In this invention, the Ti content is controlled within the range of 0.006%-0.02%.

[0017] Cu: Cu is a ferrite-strengthening element. Adding a certain amount of Cu can improve the strength and low-temperature toughness of steel through solid solution strengthening and precipitation strengthening. However, excessive Cu content can cause copper brittleness during hot working and lead to easy forging cracks at higher temperatures. This invention controls the Cu content within the range of 0.20%-0.55%.

[0018] Ni: Ni's lattice constant is similar to that of γ-iron, allowing it to form a continuous solid solution and improve the strength of steel. Simultaneously, during artificial aging, it suppresses metastable Fe carbides. 2.4 C and nitride Fe 16 The precipitation of Ni expands the austenite phase region, lowers the brittle transition temperature of the steel plate, and greatly improves the low-temperature toughness and strain aging properties of the steel plate. In this invention, the Ni content is controlled within the range of 0.3%-0.8%.

[0019] Boron (B) can replace some precious metals to improve the strength and hardenability of steel, which is beneficial to the density and hot rolling performance of thick steel plates. However, adding too much boron will greatly reduce the steel's resistance to brittle fracture. In this invention, the range of boron content is controlled to be 0.001%-0.0025%.

[0020] Al: Al mainly acts as a deoxidizer in steel, and can also form AlN precipitation, which refines the grains, fixes nitrogen in the steel, significantly improves the low-temperature impact toughness of the steel, and reduces the tendency for cold brittleness and aging. However, excessive Al content will form large oxide inclusions, resulting in high stress concentration at the inclusion sites, which will have an adverse effect on low-temperature toughness. In this invention, the Al content is controlled within the range of 0.035%-0.075%.

[0021] Hf: Hf is one of the more important elements for improving the low-temperature toughness and aging properties of steel. Compared with other microalloying elements, Hf has a stronger affinity for C and N, forming stable and insoluble fine HfC and HfN dispersed precipitates at high temperatures. These precipitates are distributed as dispersed particles within the grains, achieving ultrafine second-phase strengthening, thereby improving the strength and low-temperature toughness of the steel. The combined addition of Hf with Y, B, and Ti elements better inhibits austenite grain growth and promotes the formation of ultrafine grains than adding them alone. The combination of Hf+Nb+Ti can remove all free N elements from the solid solution, further reducing the ductile-brittle transition temperature and improving the low-temperature strain-aging toughness of the steel plate. In this invention, the range of Hf is controlled to be 0.005%-0.025%.

[0022] Zr: Under high-temperature conditions, Zr effectively inhibits grain growth. During high-temperature rolling, it forms fine carbide and nitride dispersions, while simultaneously promoting grain boundary nucleation and growth into a network structure, forming discontinuous rod-shaped carbides that hinder grain boundary slip and improve the alloy's creep strength. Furthermore, Zr is a strong deoxidizing and denitrogenating element, which is beneficial to the aging properties of the steel sheet. This invention controls the Zr content within the range of 0.3%-0.7%.

[0023] Y (Y): Y can significantly reduce the content of O and S in steel, forming compounds with higher melting points and improving the utilization rate of alloying elements such as Nb, Cu, Ti, and Hf. It forms spherical inclusions with higher melting points that are randomly distributed within the grains, eliminating the influence of type II sulfides distributed along grain boundaries on the anisotropy of the steel. Simultaneously, Y can significantly reduce the amount of carbon and nitrogen dissolved in steel, inhibiting their segregation at grain boundaries and crystal defects after dissolution, reducing the number of interstitial atoms pinning dislocations, thus improving the low-temperature toughness and aging performance of the steel. In this invention, the range of Y is controlled to be 0.015%-0.035%.

[0024] Sulfur (S): Sulfur is detrimental to the low-temperature toughness of steel. It often exists in steel in the form of FeS, which has low plasticity, increasing the brittleness of the steel. It also forms a low-melting-point eutectic with Fe at the austenite grain boundaries, making it prone to hot brittleness during processing. Excessive sulfur content during steelmaking makes it difficult to remove nitrogen (N) elements, affecting the low-temperature aging properties of the steel. This invention controls the sulfur content to ≤0.0015%.

[0025] P: During crystallization, phosphorus (P) tends to segregate within the grains, increasing the ductile-brittle transition temperature of the steel plate and causing cold brittleness, which is detrimental to the low-temperature toughness of the steel plate. This invention controls the P content to ≤0.008%.

[0026] Based on the above technical solution, the high-strength and tough low-temperature marine steel plate has a yield strength ≥460MPa, a tensile strength of 590-700MPa, an elongation ≥20%, and an impact energy of -60℃ after strain aging ≥200J.

[0027] The present invention also provides a method for manufacturing the high-strength and tough low-temperature marine steel plate with good strain aging properties, comprising the following steps: smelting step → continuous casting and billet slow cooling step → heating step → rolling step → cooling step → stacking slow cooling step.

[0028] Based on the above technical solution, further, the molten iron is deeply desulfurized before the smelting process, and the S content after desulfurization is ≤0.0015%. The smelting process includes converter smelting, LF refining and VD treatment.

[0029] Based on the above technical solution, the converter smelting adopts the double slag method to reduce the P element content in the steel to ≤0.008%; after the C content reaches the standard, alloying elements are added for deoxidation and alloying.

[0030] Based on the above technical solution, further, during the LF refining process, a reducing slag is generated to ensure an alkalinity of 4-5. During the process, bottom blowing argon agitation causes the oxide inclusions generated in the molten steel to float to the surface and be adsorbed by the slag. During the refining dust removal, the fan speed is reduced so that the top of the large ladle is filled with argon gas, reducing the exposure of the molten steel to nitrogen absorption.

[0031] Based on the above technical solution, further, the vacuum pressure holding time during the VD treatment is ≥15min, and the weak argon blowing time is ≥20min.

[0032] Based on the above technical solutions, further, in the continuous casting and billet slow cooling processes, argon gas protection is provided at the connection between the long nozzle and the immersion nozzle during continuous casting to reduce oxygen and nitrogen absorption by the molten steel; the superheat of the tundish is controlled at 19-26℃; a light reduction technique is adopted at the end of continuous casting, with a reduction of 8-13mm; and the billets after being removed from the line are stacked for slow cooling, with a stacking and slow cooling time of ≥48h.

[0033] Based on the above technical solution, further, in the heating process, the continuously cast billet adopts a four-stage heating process, with a preheating temperature of 950-1050℃ and a preheating time of 40-50 min; the first heating stage temperature is 1030-1120℃ and the heating time is 50-60 min; the second heating stage temperature is 1200-1300℃ and the heating time is 50-60 min; and the soaking stage temperature is 1150-1250℃ and the heating time is 80-90 min.

[0034] Based on the above technical solution, further, in the rolling process, the rolling process adopts a two-stage rolling with a large reduction. The first stage rolling temperature is 980-1100℃, the first pass reduction is not less than 50mm, the minimum single pass reduction rate for the remaining passes is 13-17%, and the thickness of the intermediate billet is controlled to be 2.5-3 times the thickness of the finished steel plate. The intermediate billet is water-cooled at a cooling rate of 5.0-7.0℃ / s. The second stage rolling temperature is 860-970℃, the minimum single pass reduction rate is 10-15%, and the final rolling temperature is 760-850℃.

[0035] Based on the above technical solution, further, in the cooling process, the starting cooling temperature is 670-760℃, the cooling rate is 15-25℃ / s, and the reddening temperature is 580-650℃.

[0036] Based on the above technical solution, further, in the stacking and slow cooling process, the stacking and slow cooling temperature is 330-380℃, and the stacking and slow cooling time is not less than 24 hours.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] This invention employs an ultra-low carbon composition design, using the composite addition of micro-isomorphic carbonitride forming elements such as Hf, Zr, Nb, and Ti to refine the grains, thereby improving the steel's strength, elongation, and low-temperature toughness. Simultaneously, the introduction of element Y inhibits and removes free C and N elements from the steel, enhancing its low-temperature toughness after strain aging. A purified metallurgical process is used to reduce the content of impurity elements such as S, P, O, and N. Four-stage heating, two-stage high-reduction rolling, and online rapid quenching are employed to precisely control the uniform precipitation and growth of microalloying element compounds in the steel. The final product is a high-strength, high-toughness, low-temperature marine engineering steel plate with a thickness of 60-80mm, a microstructure of fine ferrite + bainite grains, a yield strength ≥460MPa, a tensile strength of 590-700MPa, an elongation ≥20%, and an impact energy ≥200J at -60℃ after strain aging, exhibiting excellent mechanical properties and strain-aging performance. Attached Figure Description

[0039] To more clearly illustrate the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below.

[0040] Figure 1 Metallographic image (500x magnification) of a high-strength, high-toughness, low-temperature marine steel plate with good strain aging properties obtained in Example 1. Detailed Implementation

[0041] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0042] Examples 1-12

[0043] This embodiment provides a method for manufacturing a high-strength, high-toughness, low-temperature marine engineering steel plate with good strain aging performance. The chemical composition and weight percentage of the high-strength, high-toughness, low-temperature marine engineering steel plate are shown in Table 1.

[0044] Table 1. Chemical composition and weight percentage (%) of high-strength, high-toughness, low-temperature marine engineering steel plates from Examples 1-12

[0045]

[0046] Includes the following steps:

[0047] 1) Smelting process

[0048] a) After deep desulfurization, the molten iron is added to the converter and smelted using the double slag method to reduce the P content in the steel. After the C content reaches the standard, the above-mentioned alloying elements are added to the converter for deoxidation and alloying.

[0049] b) The molten steel undergoes LF refining, during which reducing slag is formed, maintaining a basicity of 4-5. Bottom-blown argon agitation is used to cause oxide inclusions generated in the molten steel to float to the surface and be adsorbed by the slag. During dust removal in the refining process, the fan speed is reduced, ensuring the ladle is filled with argon gas to minimize nitrogen absorption by exposed molten steel.

[0050] c) Perform VD treatment on the molten steel, ensure vacuum degassing time, and control the process by holding the vacuum pressure for 15 minutes + weak argon blowing for 20 minutes to promote the inclusions generated during the refining process to float into the slag, thereby minimizing the nitrogen and oxygen content.

[0051] 2) Continuous casting and billet slow cooling process: During continuous casting, argon gas protection is applied to the joints of long nozzles and immersion nozzles to reduce oxygen and nitrogen absorption by the molten steel; the superheat of the tundish is controlled as shown in Table 2; a light reduction technique is used at the end of continuous casting, and the amount of light reduction is shown in Table 2. After the billets are removed from the line, they are stacked for slow cooling, and the stacking and slow cooling time is shown in Table 2, to eliminate stress in the billets.

[0052] Table 2. Smelting and billet pretreatment parameters for high-strength, high-toughness, low-temperature marine engineering steel plates in Examples 1-12

[0053]

[0054] 3) Heating process: The continuous casting billet adopts a low-temperature four-stage heating process. The preheating temperature and time, the temperature and time of heating stage one, the temperature and time of heating stage two, and the temperature and time of soaking stage are shown in Table 3. By appropriately reducing the heating stage time, abnormal growth of the as-cast structure during the heating stage can be avoided.

[0055] Table 3 Heating process of high-strength and tough low-temperature marine steel plates in Examples 1-12

[0056]

[0057]

[0058] 4) Rolling Process: The rolling process adopts a two-stage rolling with large reduction. The initial rolling temperature, first pass reduction, reduction rate of subsequent passes, thickness ratio of intermediate billet to finished steel plate, and intermediate billet cooling rate are shown in Table 4. The intermediate billet is water-cooled to prevent further grain growth and maintain grain refinement. The initial rolling temperature, minimum single-pass reduction rate of the second stage, and final rolling temperature are shown in Table 4.

[0059] Table 4 Rolling process of high-strength, high-toughness, low-temperature marine steel plates in Examples 1-12

[0060]

[0061] 5) Cooling and slow cooling process: After rolling, an online quenching and cooling process is adopted. The starting cooling temperature, cooling rate, and reddening temperature are shown in Table 5. The slow cooling temperature and stacking time are shown in Table 5.

[0062] Table 5 Cooling process of high-strength, high-toughness, low-temperature marine steel plates in Examples 1-12

[0063]

[0064]

[0065] Finally, a high-strength, high-toughness, low-temperature marine engineering steel plate with good strain aging properties was obtained. The finished product underwent 5% plastic deformation, aging at 250℃ for 1 hour, and impact testing at -60℃. The mechanical properties of the finished steel plate and the steel plate after aging are shown in Table 6.

[0066] Table 6 Mechanical properties of high-strength, high-toughness, low-temperature marine steel plates from Examples 1-12

[0067]

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-strength, high-toughness, low-temperature marine engineering steel plate with good strain aging properties, characterized in that, The chemical composition and weight percentage of the high-strength and high-toughness low-temperature marine steel plate are as follows: C: 0.02%-0.05%, Si: 0.15%-0.45%, Mn: 1.6%-2.3%, Nb: 0.04%-0.08%, Ti: 0.006%-0.02%, Cu: 0.20%-0.55%, Ni: 0.3%-0.8%, Zr: 0.3%-0.7%, B: 0.001%-0.0025%, Al: 0.035%-0.075%, Hf: 0.005%-0.025%, Y: 0.015%-0.035%, S: ≤0.0015%, P ≤0.008%, with the remainder being iron and unavoidable impurities; The high-strength and high-toughness low-temperature marine steel plate has a yield strength ≥460MPa, tensile strength 590-700MPa, elongation ≥20%, and impact energy at -60℃ after strain aging ≥200J. The manufacturing method of the high-strength, high-toughness, low-temperature marine engineering steel plate with good strain aging properties includes the following steps: smelting process → continuous casting and billet slow cooling process → heating process → rolling process → cooling process → stacking slow cooling process, wherein, In the heating process, the continuously cast billet adopts a four-stage heating process: preheating temperature 950-1050℃, preheating time 40-50min; heating stage one temperature 1030-1120℃, heating time 50-60min; heating stage two temperature 1200-1300℃, heating time 50-60min; and soaking stage temperature 1150-1250℃, heating time 80-90min. In the rolling process, a two-stage rolling process with large reduction is adopted. The first stage starts at a rolling temperature of 980-1100℃, with a first-pass reduction of not less than 50mm, and a minimum single-pass reduction rate of 13-17% for the remaining passes. The thickness of the intermediate billet is controlled to be 2.5-3 times the thickness of the finished steel plate. The intermediate billet is water-cooled at a cooling rate of 5.0-7.0℃ / s. The second stage starts at a rolling temperature of 860-970℃, with a minimum single-pass reduction rate of 10-15%, and a final rolling temperature of 760-850℃. During the cooling process, the starting temperature is 670-760℃, the cooling rate is 15-25℃ / s, and the reddening temperature is 580-650℃. During the stacking and slow cooling process, the stacking and slow cooling temperature is 330-380℃, and the stacking and slow cooling time is not less than 24 hours.

2. The high-strength, high-toughness, low-temperature marine steel plate according to claim 1, characterized in that, The molten iron undergoes deep desulfurization before the smelting process, and the sulfur content after desulfurization is ≤0.0015%. The smelting process includes converter smelting, LF refining and VD treatment.

3. The high-strength, high-toughness, low-temperature marine steel plate according to claim 2, characterized in that, The converter smelting adopts the double slag method to reduce the P element content in the steel to ≤0.008%; after the C content reaches the standard, alloying elements are added for deoxidation and alloying.

4. The high-strength, high-toughness, low-temperature marine steel plate according to claim 2, characterized in that, During the LF refining process, a reducing slag is generated to maintain an alkalinity of 4-5, and bottom-blown argon stirring is used.

5. The high-strength, high-toughness, low-temperature marine steel plate according to claim 2, characterized in that, During VD treatment, maintain vacuum pressure for ≥15 min and perform weak argon blowing for ≥20 min.

6. The high-strength, high-toughness, low-temperature marine steel plate according to claim 1, characterized in that, In the continuous casting and billet slow cooling processes, argon gas protection is provided at the connection points of the long nozzle and immersion nozzle during continuous casting; the superheat of the tundish is controlled at 19-26℃; a light reduction technique is adopted at the end of continuous casting, with a reduction of 8-13mm; after the billet is removed from the line, it is stacked and slow cooled for ≥48h.

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