Low-temperature impact-resistant high-strength manganese-molybdenum-vanadium steel sheet and method for producing the same

Abstract

This invention relates to the field of metallurgy and metal material processing technology, specifically disclosing a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate and its production method. The steel plate is made from the following raw materials by weight percentage: C 0.08-0.14%, Si 0.18-0.35%, Mn 1.3-1.75%, Mo 0.18-0.32%, V 0.06-0.12%, Ti 0.013-0.019%, B 0.001-0.0025%, N 0.0036-0.0048%, Al 0.012-0.028%, Ca 0.001-0.003%, P≤0.008%, S 0.0005-0.0025%, with the balance being Fe and unavoidable impurities. This invention, through the synergistic effect of composite modifying slag-forming agents, calcium treatment, composition and process control, yields a steel plate with high strength and -40℃ impact energy, and good Z-axis properties.

Description

Technical Field

[0001] This invention relates to the field of metallurgy and metal material processing technology, specifically to a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate and its production method. Background Technology

[0002] High-strength steel plates for cryogenic service are widely used in marine engineering equipment, cold-region engineering structural components, cryogenic storage and transportation equipment, and high-load engineering machinery. These service scenarios typically require steel plates to possess high yield strength, good low-temperature impact toughness, stable weldability, and high resistance to lamellar tearing in the thickness direction.

[0003] For high-strength steel plates with a thickness of 20-60mm, relying solely on increasing the carbon content or alloying element content to achieve strength can easily lead to increased sensitivity to cold cracking during welding, decreased low-temperature impact toughness, and increased manufacturing costs. Furthermore, thick steel plates also present the following problems during smelting, continuous casting, and hot working: First, if sulfides, alumina inclusions, silicate inclusions, and spherical oxide inclusions in the steel are not adequately controlled, they can easily become crack initiation sites under low-temperature impact loads, reducing the steel plate's low-temperature impact absorption energy. Second, elements such as Mn and Mo tend to accumulate in the central region during thick plate preparation, forming central segregation and central porosity, affecting the thickness-direction properties of the steel plate and potentially reducing the Z-axis reduction of area. Third, conventional CaO-Al2O3 refining slags have limited adsorption, melting, and modification capabilities for high-melting-point Al2O3 inclusions and composite silicate inclusions. If the subsequent calcium treatment window is not properly controlled, insufficient calcium treatment or excessive CaS formation can easily occur, leading to unstable inclusion morphology and consequently affecting low-temperature impact toughness and thickness-direction properties. Fourth, effectively utilizing the hardenability of microalloying elements while avoiding the coarsening of harmful precipitates or inclusions is a pressing challenge. Fifth, traditional heating process parameters often fail to balance the uniformity of element diffusion and the refinement of grain size. Based on the above, this invention proposes a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate and its production method. Summary of the Invention

[0004] To address the technical challenges of low-temperature fracture induced by inclusions, weakened thickness-direction properties due to central segregation, and the difficulty in balancing strength and low-temperature toughness in existing thick-gauge high-strength steel plates, this invention proposes a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate and its production method. This invention achieves high strength, high impact energy at -40℃, and good Z-direction properties through the synergistic effects of low-carbon Mn-Mo-VB composition design, narrow-range Ti / N ratio control, Mo / V ratio control, Ca / S ratio control, refining with a BaO-MgO pre-melting composite slagging agent, VD post-calcification treatment, continuous casting dynamic light reduction, stepped temperature homogenization, and controlled rolling and cooling tempering.

[0005] In a first aspect, the present invention provides a high-strength manganese-molybdenum-vanadium steel plate resistant to low-temperature impact, employing the following technical solution: A high-strength manganese-molybdenum-vanadium steel plate resistant to low-temperature impact is made from the following raw materials in weight percentages: C 0.08-0.14%, Si 0.18-0.35%, Mn 1.3-1.75%, Mo 0.18-0.32%, V 0.06-0.12%, Ti 0.013-0.019%, B 0.001-0.0025%, N 0.0036-0.0048%, Al 0.012-0.028%, Ca 0.001-0.003%, P≤0.008%, S 0.0005-0.0025%, with the balance being Fe and unavoidable impurities.

[0006] Preferably, the weight percentage of C is 0.1-0.13%, the weight percentage of Mn is 1.45-1.65%, the weight percentage of Mo is 0.22-0.28%, and the weight percentage of V is 0.075-0.1%.

[0007] Preferably, the mass ratio of Ti to N in the raw material components satisfies: 3.45 ≤ Ti / N ≤ 3.95.

[0008] Preferably, the mass ratio of Mo to V in the raw material components satisfies: 2.2 ≤ Mo / V ≤ 3.

[0009] Preferably, the mass ratio of Ca to S in the raw material components satisfies: 0.8 ≤ Ca / S ≤ 2.

[0010] Preferably, the thickness of the steel plate is 20-60 mm.

[0011] Preferably, the total oxygen content TO ≤ 0.002% and the hydrogen content H ≤ 0.0002% of the steel plate.

[0012] Preferably, the steel plate has a yield strength ≥900MPa, tensile strength ≥1050MPa, elongation after fracture ≥15%, Charpy V-notch impact energy ≥100J at -40℃, Z-direction reduction of area ≥35%, and the highest rating of non-metallic inclusions of categories A, B, C and D is no higher than 0.5.

[0013] Secondly, this invention provides a method for producing a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate, employing the following technical solution: A method for producing a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate includes the following steps: (1) Smelting and refining: Raw materials are prepared according to weight percentage. The molten iron is smelted in a converter and then tapped into steel. The molten steel is transferred to the LF refining furnace. During the LF refining period, a pre-melted composite slag-forming agent containing BaO-MgO is added to form white slag, desulfurize, deoxidize and adsorb inclusions. In the LF refining stage, ferromolybdenum, ferrovanadium, ferrotitanium and ferroboron alloys are added to adjust Mo, V, Ti and B to the target range to obtain refined molten steel. (2) VD vacuum degassing and calcium treatment: The refined molten steel is subjected to VD vacuum degassing. After the vacuum is broken by VD, the silicon-calcium alloy wire is subjected to calcium treatment. After the calcium treatment, soft argon blowing is performed to obtain calcium-treated molten steel. (3) Continuous casting and dynamic light reduction: The calcium-treated molten steel is continuously cast into a billet, and a dynamic light reduction process is implemented at the end of the billet solidification period to obtain the billet. (4) Stepped temperature uniform heating: The steel billet is subjected to stepped temperature uniform heating treatment; (5) Rolling and heat treatment: The heated steel billet is subjected to controlled rolling, controlled cooling and tempering to obtain a high-strength manganese-molybdenum-vanadium steel plate resistant to low-temperature impact.

[0014] Preferably, in step (1), converter smelting specifically refers to: the final carbon content of converter smelting is 0.03-0.06%, the final phosphorus content is ≤0.008%, the tapping temperature is 1620-1660℃, and slag-blocking is used for tapping.

[0015] Preferably, in step (1), the LF refining temperature is 1580-1600℃, the LF refining time is 30-40min, the white slag holding time is 15-30min, and the total amount of FeO and MnO in the LF slag is ≤1%.

[0016] Preferably, in step (1), the mass percentage of the components of the BaO-MgO pre-melted composite modified slag-forming agent is: BaO 10-14%, Al2O3 28-34%, MgO 3-6%, SiO2 1-3.5%, and the balance is CaO.

[0017] Preferably, the BaO-MgO pre-melted composite modified slagging agent is prepared by the following method: Using lime, industrial alumina, quartz sand, lightly calcined magnesia, and barium carbonate as raw materials, the raw materials are calculated and proportioned according to the target oxide composition. After drying the raw materials at 180-220℃ for 1-3 hours, they are mixed evenly and melted at 1450-1500℃ for 30-45 minutes. Then, they are water-quenched and crushed, and sieved to obtain pre-melted particles with a particle size of 5-30 mm. These particles are then dried at 160-200℃ until the moisture content is ≤0.3%, thus obtaining the BaO-MgO pre-melted composite modified slagging agent.

[0018] Preferably, in step (1), the amount of BaO-MgO pre-melted composite modified slag-forming agent added is 0.8-1.2% of the total mass of molten steel.

[0019] Preferably, in step (2), vacuum degassing specifically refers to: controlling the vacuum degree to ≤67Pa, maintaining the vacuum for 12-20min, and bottom blowing argon flow rate to 25-40NL / min.

[0020] Preferably, in step (2), after the vacuum is broken by VD, the temperature of the molten steel is 1565-1585℃. Calcium treatment is performed using silicon-calcium alloy wire with a diameter of 13mm. The wire feeding speed is 180-260m / min, and the calcium treatment time is 2-4min. The weight percentage content of each component in the silicon-calcium alloy wire is as follows: Ca 28-32%, Si 55-65%, Al≤1.5%, P≤0.04%, S≤0.04%, with the remainder being Fe and unavoidable impurities. The amount of silicon-calcium alloy wire added is 0.6-1.1kg / t steel. After calcium treatment, the steel is soft-blown with argon gas at a flow rate of 15-25NL / min for 8-15min.

[0021] Preferably, in step (3), continuous casting specifically refers to: casting with argon gas protection throughout the process, controlling the superheat of molten steel in the tundish at 15-25℃, controlling the casting speed at 0.9-1.1m / min, and using gas-water atomization cooling in the secondary cooling zone with a specific water volume of 0.45-0.65L / kg.

[0022] Preferably, in step (3), the operation of the dynamic light reduction process is as follows: at the end of the secondary cooling zone of the continuous casting machine, within the range where the solid fraction at the center of the billet reaches 0.4-0.7, a light reduction of 3.5-6 mm is applied.

[0023] Preferably, in step (4), the specific operation of the stepped temperature change heating is as follows: first, heat the billet to 1140-1160℃ and hold for 1-1.5h, then heat it to 1210-1230℃ and hold for 0.5-1h, and finally cool it down to 1170-1190℃ for 0.5-1h before taking it out of the furnace.

[0024] Preferably, in step (5), controlled rolling specifically refers to: the initial rolling temperature is 1100-1150℃, the final rolling temperature is 800-850℃, and the total reduction rate is >60%.

[0025] Preferably, in step (5), controlled cooling specifically refers to cooling to 320-380℃ at a cooling rate of 24-38℃ / s.

[0026] Preferably, in step (5), tempering specifically refers to tempering at a temperature of 560-640℃ for 35-55 minutes followed by air cooling.

[0027] In summary, the present invention has the following beneficial effects: 1. This invention employs a low-carbon composition of 0.08-0.14% and improves the hardenability and post-tempering strength of thick steel plates through Mn, Mo, V, and B composite alloying. Specifically, Mo delays the transformation of ferrite and pearlite during continuous cooling; V forms carbonitride precipitates during tempering; and B, under the condition of Ti fixing N, is beneficial for improving the hardenability of the steel plate's core.

[0028] 2. The present invention controls the Ti / N ratio to 3.45-3.95, so that Ti has a sufficient fixing effect on N, while reducing the risk of the formation of coarse TiN particles caused by excessive Ti; compared with the comparative examples with Ti / N ratios that are too high or too low, this range can improve the matching between strength and impact toughness at -40℃.

[0029] 3. This invention uses a BaO-MgO pre-melted composite modified slag-forming agent for LF refining. After BaO forms a composite slag system with CaO and Al2O3, it is beneficial to improve the slag's ability to adsorb, melt, and modify Al2O3-type inclusions and silicate-type inclusions; MgO is used to adjust the slag viscosity and high-temperature stability, and reduce the fluctuation of slag system composition during the refining process.

[0030] 4. This invention involves calcium treatment of silicon-calcium alloy wire after vacuum degassing (VD), controlling the Ca / S ratio to 0.8-2. This process transforms residual high-melting-point Al2O3 inclusions into calcium aluminate composite inclusions, while simultaneously reducing the adverse effects of elongated sulfides on Z-axis properties. By combining a BaO-MgO pre-melted composite slagging agent with calcium treatment, the total oxygen content of the steel plate can be controlled below 0.002%, the hydrogen content below 0.0002%, and the highest rating of non-metallic inclusions controlled to no higher than 0.5.

[0031] 5. The present invention implements dynamic light pressure at the end of continuous casting solidification and combines it with a stepped temperature homogenization system, which can effectively improve the adverse effects of central porosity and central segregation on the Z-axis properties of steel plates.

[0032] 6. The preparation process of this invention can be implemented on a conventional high-strength steel smelting, rolling and heat treatment production line. The resulting steel plate has a yield strength ≥900MPa, tensile strength ≥1050MPa, elongation after fracture ≥15%, Charpy V-notch impact energy ≥100J at -40℃, and Z-direction reduction of area ≥35%, which can meet the comprehensive requirements of high-strength steel plates for low-temperature structures for strength, toughness and thickness direction performance. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the embodiments.

[0034] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0035] Preparation Examples 1-3 provide BaO-MgO pre-melted composite modified slagging agents Preparation Example 1 The component mass percentage of the BaO-MgO pre-melted composite modified slag-forming agent is: BaO 12%, Al2O3 31.5%, MgO 4.5%, SiO2 2.5%, with the balance being CaO.

[0036] BaO-MgO pre-melted composite modified slagging agent is prepared by the following method: Using lime, industrial alumina, quartz sand, lightly calcined magnesia, and barium carbonate as raw materials, the raw materials are formulated according to the target oxide composition. The raw materials are dried at 200℃ for 2 hours and then mixed evenly. They are then melted at 1475℃ for 38 minutes, followed by water quenching and crushing. The pre-melted particles with a particle size of 5-30 mm are obtained by sieving and drying at 180℃ to a moisture content of 0.22%, thus obtaining the BaO-MgO pre-melted composite modified slagging agent.

[0037] Preparation Example 2 The component mass percentage of the BaO-MgO pre-melted composite modified slag-forming agent is: BaO 10.5%, Al2O3 30%, MgO 3.5%, SiO2 2%, with the balance being CaO.

[0038] BaO-MgO pre-melted composite modified slagging agent is prepared by the following method: Using lime, industrial alumina, quartz sand, lightly calcined magnesia, and barium carbonate as raw materials, the raw materials are calculated and proportioned according to the target oxide composition. The raw materials are dried at 180℃ for 3 hours and then mixed evenly. They are then melted at 1450℃ for 45 minutes, followed by water quenching and crushing. The pre-melted particles with a particle size of 5-30 mm are obtained by sieving and drying at 170℃ to a moisture content of 0.25%, thus obtaining the BaO-MgO pre-melted composite modified slagging agent.

[0039] Preparation Example 3 The component mass percentage of the BaO-MgO pre-melted composite modified slag-forming agent is: BaO 13.5%, Al2O3 33%, MgO 5.5%, SiO2 3%, with the balance being CaO.

[0040] BaO-MgO pre-melted composite modified slagging agent is prepared by the following method: Using lime, industrial alumina, quartz sand, lightly calcined magnesia, and barium carbonate as raw materials, the raw materials are calculated and proportioned according to the target oxide composition. The raw materials are dried at 220℃ for 1 hour and then mixed evenly. They are then melted at 1500℃ for 30 minutes, followed by water quenching and crushing. The pre-melted particles with a particle size of 5-30 mm are obtained by sieving and drying at 200℃ to a moisture content of 0.18%, thus obtaining the BaO-MgO pre-melted composite modified slagging agent.

[0041] Comparative preparation example 1 provides a pre-melted composite modified slagging agent containing MgO. Comparative Preparation Example 1 The mass percentage of the components in the MgO-containing pre-melted composite modified slag-forming agent is: Al2O3 31.5%, MgO 4.5%, SiO2 2.5%, with the balance being CaO.

[0042] The MgO-containing pre-melted composite modified slagging agent is prepared by the following method: Using lime, industrial alumina, quartz sand, and lightly calcined magnesia as raw materials, the raw materials are formulated according to the target oxide composition. The raw materials are dried at 200℃ for 2 hours and then mixed evenly. They are then melted at 1475℃ for 38 minutes, followed by water quenching and crushing. The pre-melted particles with a particle size of 5-30 mm are obtained by sieving and drying at 180℃ to a moisture content of 0.22%, thus obtaining the MgO-containing pre-melted composite modified slagging agent.

[0043] Comparative preparation example 2 provides a BaO-pre-melted composite modified slagging agent. Comparative Preparation Example 2 The mass percentage of the components in the BaO-containing pre-melted composite modified slag-forming agent is: BaO 12%, Al2O3 31.5%, SiO2 2.5%, with the balance being CaO.

[0044] BaO-containing pre-melted composite modified slagging agent is prepared by the following method: Using lime, industrial alumina, quartz sand and barium carbonate as raw materials, the raw materials are calculated and proportioned according to the target oxide composition. The raw materials are dried at 200℃ for 2 hours and then mixed evenly. They are then melted at 1475℃ for 38 minutes, followed by water quenching and crushing. The pre-melted particles with a particle size of 5-30 mm are obtained by sieving and drying at 180℃ to a moisture content of 0.22%, thus obtaining the BaO-containing pre-melted composite modified slagging agent.

[0045] Examples 1-3 provide a low-temperature impact resistant manganese-molybdenum-vanadium high-strength steel plate and its production method.

[0046] Example 1 A low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate is made from the following raw materials by weight percentage: C 0.11%, Si 0.26%, Mn 1.55%, Mo 0.24%, V 0.09%, Ti 0.0165%, B 0.0018%, N 0.0045%, Al 0.02%, Ca 0.002%, P 0.006%, S 0.0018%, with the balance being Fe and unavoidable impurities; wherein, Ti / N=3.67, Mo / V=2.67, Ca / S=1.11.

[0047] A method for producing a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate includes the following steps: (1) Smelting and refining: Raw materials are prepared according to weight percentage, and molten iron is added to the converter for top and bottom blowing smelting. The carbon content at the end of the converter is controlled to be 0.045%, the phosphorus content at the end of the converter is 0.006%, and the tapping temperature is 1640℃. Slag-blocking tapping is adopted in the tapping process. When 1 / 3 of the steel is tapped, silicon manganese alloy, ferrosilicon and aluminum particles are added for preliminary deoxidation and basic alloying to obtain molten steel. Molten steel was transferred to an LF refining furnace and heated to 1590℃. 1% (by weight of the molten steel) of a BaO-MgO pre-melted composite slag-forming agent (prepared in Preparation Example 1) was added. During the LF refining process, the total FeO and MnO content in the slag was controlled at 0.8%, the white slag retention time was 22 min, and the total LF refining time was 35 min. In the LF refining stage, FeMo60, FeV50, FeTi70, and FeB20 were used to adjust Mo, V, Ti, and B to their target contents, respectively, to obtain refined molten steel. (2) Vacuum degassing and calcium treatment in VD furnace: The refined molten steel was transferred to a VD furnace and kept under a vacuum of 45 Pa for 16 min. During the vacuum treatment, the bottom blowing argon flow rate was 32 NL / min. After the vacuum was broken by VD, the temperature of the molten steel was controlled at 1575℃. Calcium treatment was performed using silicon-calcium alloy wire with a diameter of 13 mm. The wire feeding speed was 220 m / min, and the calcium treatment time was 3 min. The weight percentage of each component in the silicon-calcium alloy wire was as follows: Ca 30.2%, Si 59.1%, Al 0.8%, P 0.018%, S 0.012%, with the remainder being Fe and unavoidable impurities. The amount of silicon-calcium alloy wire added was 0.85 kg / t steel. After calcium treatment, the molten steel was soft-blown with argon at a flow rate of 20 NL / min for 12 min. After the VD treatment, the total oxygen content TO of the molten steel was 0.0016%, and the hydrogen content H was 0.00015%, resulting in degassed molten steel. (3) Continuous casting and dynamic light reduction: Argon gas protection is used for casting. The degassed molten steel is cast into a 100mm thick billet. The superheat of the molten steel in the tundish is controlled at 20℃ and the casting speed is controlled at 1m / min. The secondary cooling zone is cooled by gas-water atomization with a specific water volume of 0.55L / kg. At the end of the secondary cooling zone of the continuous casting machine, in the range where the solid fraction of the billet reaches 0.4-0.7, a light reduction of 4.8mm is applied. The reduction is distributed to 4 roll sections. The reduction of the 4 roll sections is 1mm, 1.2mm, 1.3mm and 1.3mm respectively to obtain the billet. (4) Step temperature uniform heating: The steel billet is loaded into the heating furnace, first heated to 1150℃ and held for 1.2h, then heated to 1220℃ and held for 0.8h, and finally cooled to 1180℃ for uniform heating for 0.8h before being taken out of the furnace to obtain the heated steel billet; (5) Rolling and heat treatment: The initial rolling temperature is controlled at 1120℃, the final rolling temperature is 830℃, and the total reduction rate is 70%. The heated steel billet is rolled to a thickness of 30mm in 6 passes to obtain the rolled steel plate. The rolled steel plate is cooled to 350℃ at a cooling rate of 32℃ / s, and then air-cooled to room temperature to obtain the cooled steel plate. The cooled steel plate is tempered at 600℃ for 45min, and then air-cooled to room temperature to obtain a 30mm thick high-strength manganese-molybdenum-vanadium steel plate resistant to low temperature impact.

[0048] Example 2 A low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate is made from the following raw materials by weight percentage: C 0.08%, Si 0.18%, Mn 1.3%, Mo 0.18%, V 0.06%, Ti 0.013%, B 0.001%, N 0.0036%, Al 0.012%, Ca 0.001%, P 0.007%, S 0.0012%, with the balance being Fe and unavoidable impurities; wherein, Ti / N=3.61, Mo / V=3, Ca / S=0.83.

[0049] A method for producing a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate includes the following steps: (1) Smelting and refining: Raw materials are prepared according to weight percentage, and molten iron is added to the converter for top and bottom blowing smelting. The carbon content at the end of the converter is controlled to be 0.03%, the phosphorus content at the end of the converter is 0.007%, and the tapping temperature is 1620℃. Slag-blocking tapping is adopted in the tapping process. When 1 / 3 of the steel is tapped, silicon manganese alloy, ferrosilicon and aluminum particles are added for preliminary deoxidation and basic alloying to obtain molten steel. Molten steel was transferred to an LF refining furnace and heated to 1580℃. 0.8% (by weight of the molten steel) of a BaO-MgO pre-melted composite slag-forming agent (prepared in Preparation Example 2) was added. During the LF refining process, the total amount of FeO and MnO in the slag was controlled at 0.6%, the white slag retention time was 15 min, and the total LF refining time was 30 min. During the LF refining stage, FeMo60, FeV50, FeTi70, and FeB20 were used to adjust Mo, V, Ti, and B to their target contents, respectively, to obtain refined molten steel. (2) Vacuum degassing and calcium treatment in VD furnace: The refined molten steel is transferred to a VD furnace and kept under a vacuum of 67 Pa for 12 min. During the vacuum treatment, the bottom blowing argon flow rate is 25 NL / min. After the vacuum is broken by VD, the temperature of the molten steel is controlled at 1565℃. Calcium treatment is performed using silicon-calcium alloy wire with a diameter of 13 mm. The wire feeding speed is 180 m / min, and the calcium treatment time is 4 min. The weight percentage content of each component in the silicon-calcium alloy wire is as follows: Ca 28.6%, Si 56.8%, Al 1.10%, P 0.021%, S 0.016%, with the remainder being Fe and unavoidable impurities. The amount of silicon-calcium alloy wire added is 0.6 kg / t steel. After calcium treatment, soft blowing is performed at an argon flow rate of 15 NL / min for 15 min. After the VD treatment, the total oxygen content TO of the molten steel is 0.0018%, and the hydrogen content H is 0.00016%, resulting in degassed molten steel. (3) Continuous casting and dynamic light reduction: Argon gas protection is used for casting. The degassed molten steel is cast into a 90mm thick billet. The superheat of the molten steel in the tundish is controlled at 15℃ and the casting speed is controlled at 1.1m / min. The secondary cooling zone adopts gas-water atomization cooling with a specific water volume of 0.65L / kg. At the end of the secondary cooling zone of the continuous casting machine, in the range where the solid fraction of the billet reaches 0.4-0.7, a light reduction of 3.5mm is applied. The reduction is distributed to 4 roll sections. The reduction of the 4 roll sections is 0.7mm, 0.8mm, 0.9mm and 1.1mm respectively to obtain the steel billet. (4) Step temperature uniform heating: The steel billet is loaded into the heating furnace, first heated to 1140℃ and held for 1.5h, then heated to 1210℃ and held for 1h, and finally cooled to 1170℃ and uniformly heated for 1h before being taken out of the furnace to obtain the heated steel billet. (5) Rolling and heat treatment: The initial rolling temperature is controlled at 1100℃, the final rolling temperature is 800℃, and the total reduction rate is 77.8%. The heated billet is rolled to 20mm in 6 passes to obtain the rolled steel plate. The rolled steel plate is cooled to 320℃ at a cooling rate of 38℃ / s, and then air-cooled to room temperature to obtain the cooled steel plate. The cooled steel plate is tempered at 560℃ for 55min, and then air-cooled to room temperature to obtain a 20mm thick high-strength manganese-molybdenum-vanadium steel plate resistant to low-temperature impact.

[0050] Example 3 A low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate is made from the following raw materials by weight percentage: C 0.14%, Si 0.35%, Mn 1.75%, Mo 0.32%, V 0.12%, Ti 0.0188%, B 0.0025%, N 0.0048%, Al 0.028%, Ca 0.003%, P 0.005%, S 0.0015%, with the balance being Fe and unavoidable impurities; wherein, Ti / N=3.92, Mo / V=2.67, Ca / S=2.

[0051] A method for producing a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate includes the following steps: (1) Smelting and refining: Raw materials are prepared according to weight percentage, and molten iron is added to the converter for top and bottom blowing smelting. The carbon content at the end of the converter is controlled to be 0.06%, the phosphorus content at the end of the converter is 0.005%, and the tapping temperature is 1660℃. Slag-blocking tapping is adopted in the tapping process. When 1 / 3 of the steel is tapped, silicon manganese alloy, ferrosilicon and aluminum particles are added for preliminary deoxidation and basic alloying to obtain molten steel. Molten steel was transferred to an LF refining furnace and heated to 1600℃. 1.2% (by weight of the molten steel) of a BaO-MgO pre-melted composite slag-forming agent (prepared in Preparation Example 3) was added. During the LF refining process, the total amount of FeO and MnO in the slag was controlled at 1.0%, the white slag retention time was 30 min, and the total LF refining time was 40 min. In the LF refining stage, FeMo60, FeV50, FeTi70, and FeB20 were used to adjust Mo, V, Ti, and B to the target contents, respectively, to obtain refined molten steel. (2) Vacuum degassing and calcium treatment in VD furnace: The refined molten steel is transferred to a VD furnace and kept under a vacuum of 40 Pa for 20 min. During the vacuum treatment, the bottom blowing argon flow rate is 40 NL / min. After the vacuum is broken by VD, the temperature of the molten steel is controlled at 1585℃. Calcium treatment is performed using silicon-calcium alloy wire with a diameter of 13 mm. The wire feeding speed is 260 m / min, and the calcium treatment time is 2 min. The weight percentage content of each component in the silicon-calcium alloy wire is as follows: Ca 31.5%, Si 63%, Al 0.6%, P 0.015%, S 0.01%, with the remainder being Fe and unavoidable impurities. The amount of silicon-calcium alloy wire added is 1.1 kg / t steel. After calcium treatment, soft blowing is performed at an argon flow rate of 25 NL / min for 8 min. After the VD treatment, the total oxygen content TO of the molten steel is 0.0015%, and the hydrogen content H is 0.00014%, resulting in degassed molten steel. (3) Continuous casting and dynamic light reduction: Argon gas protection is used for casting. The degassed molten steel is cast into a 160mm thick billet. The superheat of the molten steel in the tundish is controlled at 25℃ and the casting speed is controlled at 0.9m / min. The secondary cooling zone adopts gas-water atomization cooling with a specific water volume of 0.45L / kg. At the end of the secondary cooling zone of the continuous casting machine, in the range where the solid fraction of the billet reaches 0.4-0.7, a light reduction of 6mm is applied. The reduction is distributed to 4 roll sections. The reduction of the 4 roll sections is 1.2mm, 1.4mm, 1.6mm and 1.8mm respectively to obtain the steel billet. (4) Step temperature uniform heating: The steel billet is loaded into the heating furnace, first heated to 1160℃ and held for 1 hour, then heated to 1230℃ and held for 0.5 hours, and finally cooled to 1190℃ and uniformly heated for 0.5 hours before being taken out of the furnace to obtain the heated steel billet. (5) Rolling and heat treatment: The initial rolling temperature is controlled at 1150℃, the final rolling temperature is 850℃, and the total reduction rate is 62.5%. The heated billet is rolled to 60mm in 6 passes to obtain the rolled steel plate. The rolled steel plate is cooled to 380℃ at a cooling rate of 24℃ / s, and then air-cooled to room temperature to obtain the cooled steel plate. The cooled steel plate is tempered at 640℃ for 35min, and then air-cooled to room temperature to obtain a 60mm thick high-strength manganese-molybdenum-vanadium steel plate resistant to low-temperature impact.

[0052] To verify the comprehensive performance of the low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate provided by the present invention, comparative examples 1-8 were set up, wherein: Comparative Example 1 Comparative Example 1 is the same as Example 1, except that the BaO-MgO pre-melted composite modified slagging agent prepared in Preparation Example 1 is replaced by an equal mass of the MgO pre-melted composite modified slagging agent prepared in Comparative Preparation Example 1. Specifically: A low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate is made from the following raw materials by weight percentage: C 0.11%, Si 0.26%, Mn 1.55%, Mo 0.24%, V 0.09%, Ti 0.0165%, B 0.0018%, N 0.0045%, Al 0.02%, Ca 0.002%, P 0.006%, S 0.0018%, with the balance being Fe and unavoidable impurities; wherein, Ti / N=3.67, Mo / V=2.67, Ca / S=1.11.

[0053] A method for producing a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate includes the following steps: (1) Smelting and refining: Raw materials are prepared according to weight percentage, and molten iron is added to the converter for top and bottom blowing smelting. The carbon content at the end of the converter is controlled to be 0.045%, the phosphorus content at the end of the converter is 0.006%, and the tapping temperature is 1640℃. Slag-blocking tapping is adopted in the tapping process. When 1 / 3 of the steel is tapped, silicon manganese alloy, ferrosilicon and aluminum particles are added for preliminary deoxidation and basic alloying to obtain molten steel. Molten steel was transferred to an LF refining furnace and heated to 1590°C. 1% (by weight of the molten steel) of a MgO-containing pre-melted composite slag-forming agent (prepared from Comparative Preparation Example 1) was added. During the LF refining process, the total FeO and MnO content in the slag was controlled at 0.8%, the white slag retention time was 22 min, and the total LF refining time was 35 min. In the LF refining stage, FeMo60, FeV50, FeTi70, and FeB20 were used to adjust Mo, V, Ti, and B to their target contents, respectively, to obtain refined molten steel. (2) Vacuum degassing and calcium treatment in VD furnace: The refined molten steel was transferred to a VD furnace and kept under a vacuum of 45 Pa for 16 min. During the vacuum treatment, the bottom blowing argon flow rate was 32 NL / min. After the vacuum was broken by VD, the temperature of the molten steel was controlled at 1575℃. Calcium treatment was performed using silicon-calcium alloy wire with a diameter of 13 mm. The wire feeding speed was 220 m / min, and the calcium treatment time was 3 min. The weight percentage content of each component in the silicon-calcium alloy wire was as follows: Ca 30.2%, Si 59.1%, Al 0.8%, P 0.018%, S 0.012%, with the remainder being Fe and unavoidable impurities. The amount of silicon-calcium alloy wire added was 0.85 kg / t steel. After calcium treatment, the molten steel was soft-blown with argon at a flow rate of 20 NL / min for 12 min. After the VD treatment, the total oxygen content TO of the molten steel was 0.0021%, and the hydrogen content H was 0.00015%, resulting in degassed molten steel. (3) Continuous casting and dynamic light reduction: Argon gas protection is used for casting. The degassed molten steel is cast into a 100mm thick billet. The superheat of the molten steel in the tundish is controlled at 20℃ and the casting speed is controlled at 1m / min. The secondary cooling zone is cooled by gas-water atomization with a specific water volume of 0.55L / kg. At the end of the secondary cooling zone of the continuous casting machine, in the range where the solid fraction of the billet reaches 0.4-0.7, a light reduction of 4.8mm is applied. The reduction is distributed to 4 roll sections. The reduction of the 4 roll sections is 1mm, 1.2mm, 1.3mm and 1.3mm respectively to obtain the billet. (4) Step temperature uniform heating: The steel billet is loaded into the heating furnace, first heated to 1150℃ and held for 1.2h, then heated to 1220℃ and held for 0.8h, and finally cooled to 1180℃ for uniform heating for 0.8h before being taken out of the furnace to obtain the heated steel billet; (5) Rolling and heat treatment: The initial rolling temperature is controlled at 1120℃, the final rolling temperature is 830℃, and the total reduction rate is 70%. The heated steel billet is rolled to a thickness of 30mm in 6 passes to obtain the rolled steel plate. The rolled steel plate is cooled to 350℃ at a cooling rate of 32℃ / s, and then air-cooled to room temperature to obtain the cooled steel plate. The cooled steel plate is tempered at 600℃ for 45min, and then air-cooled to room temperature to obtain a 30mm thick high-strength manganese-molybdenum-vanadium steel plate resistant to low temperature impact.

[0054] Comparative Example 2 Comparative Example 2 is the same as Example 1, except that the BaO-MgO pre-melted composite modified slagging agent prepared in Preparation Example 1 is replaced by an equal mass of the BaO pre-melted composite modified slagging agent prepared in Comparative Preparation Example 2. Specifically: A low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate is made from the following raw materials by weight percentage: C 0.11%, Si 0.26%, Mn 1.55%, Mo 0.24%, V 0.09%, Ti 0.0165%, B 0.0018%, N 0.0045%, Al 0.02%, Ca 0.002%, P 0.006%, S 0.0018%, with the balance being Fe and unavoidable impurities; wherein, Ti / N=3.67, Mo / V=2.67, Ca / S=1.11.

[0055] A method for producing a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate includes the following steps: (1) Smelting and refining: Raw materials are prepared according to weight percentage, and molten iron is added to the converter for top and bottom blowing smelting. The carbon content at the end of the converter is controlled to be 0.045%, the phosphorus content at the end of the converter is 0.006%, and the tapping temperature is 1640℃. Slag-blocking tapping is adopted in the tapping process. When 1 / 3 of the steel is tapped, silicon manganese alloy, ferrosilicon and aluminum particles are added for preliminary deoxidation and basic alloying to obtain molten steel. Molten steel was transferred to an LF refining furnace and heated to 1590°C. 1% (by weight of the molten steel) of a BaO-containing pre-melted composite slag-forming agent (prepared from Comparative Preparation Example 2) was added. During the LF refining process, the total FeO and MnO content in the slag was controlled at 0.8%, the white slag retention time was 22 min, and the total LF refining time was 35 min. In the LF refining stage, FeMo60, FeV50, FeTi70, and FeB20 were used to adjust Mo, V, Ti, and B to their target contents, respectively, to obtain refined molten steel. (2) Vacuum degassing and calcium treatment in VD furnace: The refined molten steel was transferred to a VD furnace and kept under a vacuum of 45 Pa for 16 min. During the vacuum treatment, the bottom blowing argon flow rate was 32 NL / min. After the vacuum was broken by VD, the temperature of the molten steel was controlled at 1575℃. Calcium treatment was performed using silicon-calcium alloy wire with a diameter of 13 mm. The wire feeding speed was 220 m / min, and the calcium treatment time was 3 min. The weight percentage of each component in the silicon-calcium alloy wire was as follows: Ca 30.2%, Si 59.1%, Al 0.8%, P 0.018%, S 0.012%, with the remainder being Fe and unavoidable impurities. The amount of silicon-calcium alloy wire added was 0.85 kg / t steel. After calcium treatment, the molten steel was soft-blown with argon at a flow rate of 20 NL / min for 12 min. After the VD treatment, the total oxygen content TO was 0.0022%, and the hydrogen content H was 0.00016%, resulting in degassed molten steel. (3) Continuous casting and dynamic light reduction: Argon gas protection is used for casting. The degassed molten steel is cast into a 100mm thick billet. The superheat of the molten steel in the tundish is controlled at 20℃ and the casting speed is controlled at 1m / min. The secondary cooling zone is cooled by gas-water atomization with a specific water volume of 0.55L / kg. At the end of the secondary cooling zone of the continuous casting machine, in the range where the solid fraction of the billet reaches 0.4-0.7, a light reduction of 4.8mm is applied. The reduction is distributed to 4 roll sections. The reduction of the 4 roll sections is 1mm, 1.2mm, 1.3mm and 1.3mm respectively to obtain the billet. (4) Step temperature uniform heating: The steel billet is loaded into the heating furnace, first heated to 1150℃ and held for 1.2h, then heated to 1220℃ and held for 0.8h, and finally cooled to 1180℃ for uniform heating for 0.8h before being taken out of the furnace to obtain the heated steel billet; (5) Rolling and heat treatment: The initial rolling temperature is controlled at 1120℃, the final rolling temperature is 830℃, and the total reduction rate is 70%. The heated steel billet is rolled to a thickness of 30mm in 6 passes to obtain the rolled steel plate. The rolled steel plate is cooled to 350℃ at a cooling rate of 32℃ / s, and then air-cooled to room temperature to obtain the cooled steel plate. The cooled steel plate is tempered at 600℃ for 45min, and then air-cooled to room temperature to obtain a 30mm thick high-strength manganese-molybdenum-vanadium steel plate resistant to low temperature impact.

[0056] Comparative Example 3 Comparative Example 3 is the same as Example 1, except that the silicon-calcium alloy wire was not subjected to calcium treatment after vacuum de-drying. Details are as follows: A low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate is made from the following raw materials by weight percentage: C 0.11%, Si 0.26%, Mn 1.55%, Mo 0.24%, V 0.09%, Ti 0.0165%, B 0.0018%, N 0.0045%, Al 0.02%, Ca 0.0003%, P 0.006%, S 0.0018%, with the balance being Fe and unavoidable impurities; wherein, Ti / N=3.67, Mo / V=2.67, Ca / S=0.17.

[0057] A method for producing a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate includes the following steps: (1) Smelting and refining: Raw materials are prepared according to weight percentage, and molten iron is added to the converter for top and bottom blowing smelting. The carbon content at the end of the converter is controlled to be 0.045%, the phosphorus content at the end of the converter is 0.006%, and the tapping temperature is 1640℃. Slag-blocking tapping is adopted in the tapping process. When 1 / 3 of the steel is tapped, silicon manganese alloy, ferrosilicon and aluminum particles are added for preliminary deoxidation and basic alloying to obtain molten steel. Molten steel was transferred to an LF refining furnace and heated to 1590℃. 1% (by weight of the molten steel) of a BaO-MgO pre-melted composite slag-forming agent (prepared in Preparation Example 1) was added. During the LF refining process, the total FeO and MnO content in the slag was controlled at 0.8%, the white slag retention time was 22 min, and the total LF refining time was 35 min. In the LF refining stage, FeMo60, FeV50, FeTi70, and FeB20 were used to adjust Mo, V, Ti, and B to their target contents, respectively, to obtain refined molten steel. (2) Vacuum degassing in VD: The refined molten steel is transferred into the VD furnace and kept under a vacuum of 45 Pa for 16 min. During the vacuum treatment, the bottom blowing argon flow rate is 32 NL / min. After the vacuum is broken by VD, the temperature of the molten steel is controlled at 1575℃ and soft blowing is carried out at an argon flow rate of 20 NL / min for 12 min. After the VD treatment, the total oxygen content TO of the molten steel is 0.0017%, the hydrogen content H is 0.00015%, and the Ca content in the steel is 0.0003%, thus obtaining the degassed molten steel. (3) Continuous casting and dynamic light reduction: Argon gas protection is used for casting. The degassed molten steel is cast into a 100mm thick billet. The superheat of the molten steel in the tundish is controlled at 20℃ and the casting speed is controlled at 1m / min. The secondary cooling zone is cooled by gas-water atomization with a specific water volume of 0.55L / kg. At the end of the secondary cooling zone of the continuous casting machine, in the range where the solid fraction of the billet reaches 0.4-0.7, a light reduction of 4.8mm is applied. The reduction is distributed to 4 roll sections. The reduction of the 4 roll sections is 1mm, 1.2mm, 1.3mm and 1.3mm respectively to obtain the billet. (4) Step temperature uniform heating: The steel billet is loaded into the heating furnace, first heated to 1150℃ and held for 1.2h, then heated to 1220℃ and held for 0.8h, and finally cooled to 1180℃ for uniform heating for 0.8h before being taken out of the furnace to obtain the heated steel billet; (5) Rolling and heat treatment: The initial rolling temperature is controlled at 1120℃, the final rolling temperature is 830℃, and the total reduction rate is 70%. The heated steel billet is rolled to a thickness of 30mm in 6 passes to obtain the rolled steel plate. The rolled steel plate is cooled to 350℃ at a cooling rate of 32℃ / s, and then air-cooled to room temperature to obtain the cooled steel plate. The cooled steel plate is tempered at 600℃ for 45min, and then air-cooled to room temperature to obtain a 30mm thick high-strength manganese-molybdenum-vanadium steel plate resistant to low temperature impact.

[0058] Comparative Example 4 Comparative Example 4 is the same as Example 1, except that dynamic light pressure is not applied during the continuous casting process. Details are as follows: A low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate is made from the following raw materials by weight percentage: C 0.11%, Si 0.26%, Mn 1.55%, Mo 0.24%, V 0.09%, Ti 0.0165%, B 0.0018%, N 0.0045%, Al 0.02%, Ca 0.002%, P 0.006%, S 0.0018%, with the balance being Fe and unavoidable impurities; wherein, Ti / N=3.67, Mo / V=2.67, Ca / S=1.11.

[0059] A method for producing a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate includes the following steps: (1) Smelting and refining: Raw materials are prepared according to weight percentage, and molten iron is added to the converter for top and bottom blowing smelting. The carbon content at the end of the converter is controlled to be 0.045%, the phosphorus content at the end of the converter is 0.006%, and the tapping temperature is 1640℃. Slag-blocking tapping is adopted in the tapping process. When 1 / 3 of the steel is tapped, silicon manganese alloy, ferrosilicon and aluminum particles are added for preliminary deoxidation and basic alloying to obtain molten steel. Molten steel was transferred to an LF refining furnace and heated to 1590℃. 1% (by weight of the molten steel) of a BaO-MgO pre-melted composite slag-forming agent (prepared in Preparation Example 1) was added. During the LF refining process, the total FeO and MnO content in the slag was controlled at 0.8%, the white slag retention time was 22 min, and the total LF refining time was 35 min. In the LF refining stage, FeMo60, FeV50, FeTi70, and FeB20 were used to adjust Mo, V, Ti, and B to their target contents, respectively, to obtain refined molten steel. (2) Vacuum degassing and calcium treatment in VD furnace: The refined molten steel was transferred to a VD furnace and kept under a vacuum of 45 Pa for 16 min. During the vacuum treatment, the bottom blowing argon flow rate was 32 NL / min. After the vacuum was broken by VD, the temperature of the molten steel was controlled at 1575℃. Calcium treatment was performed using silicon-calcium alloy wire with a diameter of 13 mm. The wire feeding speed was 220 m / min, and the calcium treatment time was 3 min. The weight percentage of each component in the silicon-calcium alloy wire was as follows: Ca 30.2%, Si 59.1%, Al 0.8%, P 0.018%, S 0.012%, with the remainder being Fe and unavoidable impurities. The amount of silicon-calcium alloy wire added was 0.85 kg / t steel. After calcium treatment, the molten steel was soft-blown with argon at a flow rate of 20 NL / min for 12 min. After the VD treatment, the total oxygen content TO of the molten steel was 0.0016%, and the hydrogen content H was 0.00015%, resulting in degassed molten steel. (3) Continuous casting: Argon gas is used for the whole process of casting. The degassed molten steel is cast into a 100mm thick billet. The superheat of the molten steel in the tundish is controlled at 20℃, the casting speed is controlled at 1m / min, and the secondary cooling zone is cooled by gas-water atomization with a specific water volume of 0.55L / kg to obtain the billet. (4) Step temperature uniform heating: The steel billet is loaded into the heating furnace, first heated to 1150℃ and held for 1.2h, then heated to 1220℃ and held for 0.8h, and finally cooled to 1180℃ for uniform heating for 0.8h before being taken out of the furnace to obtain the heated steel billet; (5) Rolling and heat treatment: The initial rolling temperature is controlled at 1120℃, the final rolling temperature is 830℃, and the total reduction rate is 70%. The heated steel billet is rolled to a thickness of 30mm in 6 passes to obtain the rolled steel plate. The rolled steel plate is cooled to 350℃ at a cooling rate of 32℃ / s, and then air-cooled to room temperature to obtain the cooled steel plate. The cooled steel plate is tempered at 600℃ for 45min, and then air-cooled to room temperature to obtain a 30mm thick high-strength manganese-molybdenum-vanadium steel plate resistant to low temperature impact.

[0060] Comparative Example 5 Comparative Example 5 is the same as Example 1, except that the stepped temperature change heating process is replaced with conventional constant temperature heating. Details are as follows: A low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate is made from the following raw materials by weight percentage: C 0.11%, Si 0.26%, Mn 1.55%, Mo 0.24%, V 0.09%, Ti 0.0165%, B 0.0018%, N 0.0045%, Al 0.02%, Ca 0.002%, P 0.006%, S 0.0018%, with the balance being Fe and unavoidable impurities; wherein, Ti / N=3.67, Mo / V=2.67, Ca / S=1.11.

[0061] A method for producing a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate includes the following steps: (1) Smelting and refining: Raw materials are prepared according to weight percentage, and molten iron is added to the converter for top and bottom blowing smelting. The carbon content at the end of the converter is controlled to be 0.045%, the phosphorus content at the end of the converter is 0.006%, and the tapping temperature is 1640℃. Slag-blocking tapping is adopted in the tapping process. When 1 / 3 of the steel is tapped, silicon manganese alloy, ferrosilicon and aluminum particles are added for preliminary deoxidation and basic alloying to obtain molten steel. Molten steel was transferred to an LF refining furnace and heated to 1590℃. 1% (by weight of the molten steel) of a BaO-MgO pre-melted composite slag-forming agent (prepared in Preparation Example 1) was added. During the LF refining process, the total FeO and MnO content in the slag was controlled at 0.8%, the white slag retention time was 22 min, and the total LF refining time was 35 min. In the LF refining stage, FeMo60, FeV50, FeTi70, and FeB20 were used to adjust Mo, V, Ti, and B to their target contents, respectively, to obtain refined molten steel. (2) Vacuum degassing and calcium treatment in VD furnace: The refined molten steel was transferred to a VD furnace and kept under a vacuum of 45 Pa for 16 min. During the vacuum treatment, the bottom blowing argon flow rate was 32 NL / min. After the vacuum was broken by VD, the temperature of the molten steel was controlled at 1575℃. Calcium treatment was performed using silicon-calcium alloy wire with a diameter of 13 mm. The wire feeding speed was 220 m / min, and the calcium treatment time was 3 min. The weight percentage of each component in the silicon-calcium alloy wire was as follows: Ca 30.2%, Si 59.1%, Al 0.8%, P 0.018%, S 0.012%, with the remainder being Fe and unavoidable impurities. The amount of silicon-calcium alloy wire added was 0.85 kg / t steel. After calcium treatment, the molten steel was soft-blown with argon at a flow rate of 20 NL / min for 12 min. After the VD treatment, the total oxygen content TO of the molten steel was 0.0016%, and the hydrogen content H was 0.00015%, resulting in degassed molten steel. (3) Continuous casting and dynamic light reduction: Argon gas protection is used for casting. The degassed molten steel is cast into a 100mm thick billet. The superheat of the molten steel in the tundish is controlled at 20℃ and the casting speed is controlled at 1m / min. The secondary cooling zone is cooled by gas-water atomization with a specific water volume of 0.55L / kg. At the end of the secondary cooling zone of the continuous casting machine, in the range where the solid fraction of the billet reaches 0.4-0.7, a light reduction of 4.8mm is applied. The reduction is distributed to 4 roll sections. The reduction of the 4 roll sections is 1mm, 1.2mm, 1.3mm and 1.3mm respectively to obtain the billet. (4) Constant temperature heating: The steel billet is loaded into the heating furnace, heated to 1180℃ and kept at that temperature for 2.5h before being taken out of the furnace to obtain the heated steel billet; (5) Rolling and heat treatment: The initial rolling temperature is controlled at 1120℃, the final rolling temperature is 830℃, and the total reduction rate is 70%. The heated steel billet is rolled to a thickness of 30mm in 6 passes to obtain the rolled steel plate. The rolled steel plate is cooled to 350℃ at a cooling rate of 32℃ / s, and then air-cooled to room temperature to obtain the cooled steel plate. The cooled steel plate is tempered at 600℃ for 45min, and then air-cooled to room temperature to obtain a 30mm thick high-strength manganese-molybdenum-vanadium steel plate resistant to low temperature impact.

[0062] Comparative Example 6 Comparative Example 6 is the same as Example 1, except that Mo was not added to its composition. Details are as follows: A high-strength manganese-vanadium steel plate resistant to low-temperature impact is made from the following raw materials by weight percentage: C 0.11%, Si 0.26%, Mn 1.55%, V 0.09%, Ti 0.0165%, B 0.0018%, N 0.0045%, Al 0.02%, Ca 0.002%, P 0.006%, S 0.0018%, with the balance being Fe and unavoidable impurities; wherein, Ti / N=3.67, Ca / S=1.11.

[0063] A method for producing a low-temperature impact-resistant high-strength manganese-vanadium steel plate includes the following steps: (1) Smelting and refining: Raw materials are prepared according to weight percentage, and molten iron is added to the converter for top and bottom blowing smelting. The carbon content at the end of the converter is controlled to be 0.045%, the phosphorus content at the end of the converter is 0.006%, and the tapping temperature is 1640℃. Slag-blocking tapping is adopted in the tapping process. When 1 / 3 of the steel is tapped, silicon manganese alloy, ferrosilicon and aluminum particles are added for preliminary deoxidation and basic alloying to obtain molten steel. Molten steel was transferred to an LF refining furnace and heated to 1590℃. 1% (by weight of the molten steel) of a BaO-MgO pre-melted composite slag-forming agent (prepared in Preparation Example 1) was added. During the LF refining process, the total FeO and MnO content in the slag was controlled at 0.8%, the white slag retention time was 22 min, and the total LF refining time was 35 min. In the LF refining stage, FeV50 and FeTi70 were used to adjust V and Ti to their target contents, respectively, to obtain refined molten steel. (2) Vacuum degassing and calcium treatment in VD furnace: The refined molten steel was transferred to a VD furnace and kept under a vacuum of 45 Pa for 16 min. During the vacuum treatment, the bottom blowing argon flow rate was 32 NL / min. After the vacuum was broken by VD, the temperature of the molten steel was controlled at 1575℃. Calcium treatment was performed using silicon-calcium alloy wire with a diameter of 13 mm. The wire feeding speed was 220 m / min, and the calcium treatment time was 3 min. The weight percentage of each component in the silicon-calcium alloy wire was as follows: Ca 30.2%, Si 59.1%, Al 0.8%, P 0.018%, S 0.012%, with the remainder being Fe and unavoidable impurities. The amount of silicon-calcium alloy wire added was 0.85 kg / t steel. After calcium treatment, the molten steel was soft-blown with argon at a flow rate of 20 NL / min for 12 min. After the VD treatment, the total oxygen content TO of the molten steel was 0.0016%, and the hydrogen content H was 0.00015%, resulting in degassed molten steel. (3) Continuous casting and dynamic light reduction: Argon gas protection is used for casting. The degassed molten steel is cast into a 100mm thick billet. The superheat of the molten steel in the tundish is controlled at 20℃ and the casting speed is controlled at 1m / min. The secondary cooling zone is cooled by gas-water atomization with a specific water volume of 0.55L / kg. At the end of the secondary cooling zone of the continuous casting machine, in the range where the solid fraction of the billet reaches 0.4-0.7, a light reduction of 4.8mm is applied. The reduction is distributed to 4 roll sections. The reduction of the 4 roll sections is 1mm, 1.2mm, 1.3mm and 1.3mm respectively to obtain the billet. (4) Step temperature uniform heating: The steel billet is loaded into the heating furnace, first heated to 1150℃ and held for 1.2h, then heated to 1220℃ and held for 0.8h, and finally cooled to 1180℃ for uniform heating for 0.8h before being taken out of the furnace to obtain the heated steel billet; (5) Rolling and heat treatment: The initial rolling temperature is controlled at 1120℃, the final rolling temperature is 830℃, and the total reduction rate is 70%. The heated steel billet is rolled to a thickness of 30mm in 6 passes to obtain the rolled steel plate. The rolled steel plate is cooled to 350℃ at a cooling rate of 32℃ / s, and then air-cooled to room temperature to obtain the cooled steel plate. The cooled steel plate is tempered at 600℃ for 45min, and then air-cooled to room temperature to obtain a 30mm thick manganese vanadium high-strength steel plate resistant to low temperature impact.

[0064] Comparative Example 7 Comparative Example 7 is the same as Example 1, except that the Ti content is higher, resulting in a Ti / N ratio of 5.2. Details are as follows: A high-strength manganese-molybdenum-vanadium steel plate resistant to low-temperature impact is made from the following raw materials by weight percentage: C 0.11%, Si 0.26%, Mn 1.55%, Mo 0.24%, V 0.09%, Ti 0.0234%, B 0.0018%, N 0.0045%, Al 0.02%, Ca 0.002%, P 0.006%, S 0.0018%, with the balance being Fe and unavoidable impurities; wherein, Ti / N=5.2, Mo / V=2.67, Ca / S=1.11.

[0065] A method for producing a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate includes the following steps: (1) Smelting and refining: Raw materials are prepared according to weight percentage, and molten iron is added to the converter for top and bottom blowing smelting. The carbon content at the end of the converter is controlled to be 0.045%, the phosphorus content at the end of the converter is 0.006%, and the tapping temperature is 1640℃. Slag-blocking tapping is adopted in the tapping process. When 1 / 3 of the steel is tapped, silicon manganese alloy, ferrosilicon and aluminum particles are added for preliminary deoxidation and basic alloying to obtain molten steel. Molten steel was transferred to an LF refining furnace and heated to 1590℃. 1% (by weight of the molten steel) of a BaO-MgO pre-melted composite slag-forming agent (prepared in Preparation Example 1) was added. During the LF refining process, the total FeO and MnO content in the slag was controlled at 0.8%, the white slag retention time was 22 min, and the total LF refining time was 35 min. In the LF refining stage, FeMo60, FeV50, FeTi70, and FeB20 were used to adjust Mo, V, Ti, and B to their target contents, respectively, to obtain refined molten steel. (2) Vacuum degassing and calcium treatment in VD furnace: The refined molten steel was transferred to a VD furnace and kept under a vacuum of 45 Pa for 16 min. During the vacuum treatment, the bottom blowing argon flow rate was 32 NL / min. After the vacuum was broken by VD, the temperature of the molten steel was controlled at 1575℃. Calcium treatment was performed using silicon-calcium alloy wire with a diameter of 13 mm. The wire feeding speed was 220 m / min, and the calcium treatment time was 3 min. The weight percentage of each component in the silicon-calcium alloy wire was as follows: Ca 30.2%, Si 59.1%, Al 0.8%, P 0.018%, S 0.012%, with the remainder being Fe and unavoidable impurities. The amount of silicon-calcium alloy wire added was 0.85 kg / t steel. After calcium treatment, the molten steel was soft-blown with argon at a flow rate of 20 NL / min for 12 min. After the VD treatment, the total oxygen content TO of the molten steel was 0.0016%, and the hydrogen content H was 0.00015%, resulting in degassed molten steel. (3) Continuous casting and dynamic light reduction: Argon gas protection is used for casting. The degassed molten steel is cast into a 100mm thick billet. The superheat of the molten steel in the tundish is controlled at 20℃ and the casting speed is controlled at 1m / min. The secondary cooling zone is cooled by gas-water atomization with a specific water volume of 0.55L / kg. At the end of the secondary cooling zone of the continuous casting machine, in the range where the solid fraction of the billet reaches 0.4-0.7, a light reduction of 4.8mm is applied. The reduction is distributed to 4 roll sections. The reduction of the 4 roll sections is 1mm, 1.2mm, 1.3mm and 1.3mm respectively to obtain the billet. (4) Step temperature uniform heating: The steel billet is loaded into the heating furnace, first heated to 1150℃ and held for 1.2h, then heated to 1220℃ and held for 0.8h, and finally cooled to 1180℃ for uniform heating for 0.8h before being taken out of the furnace to obtain the heated steel billet; (5) Rolling and heat treatment: The initial rolling temperature is controlled at 1120℃, the final rolling temperature is 830℃, and the total reduction rate is 70%. The heated steel billet is rolled to a thickness of 30mm in 6 passes to obtain the rolled steel plate. The rolled steel plate is cooled to 350℃ at a cooling rate of 32℃ / s, and then air-cooled to room temperature to obtain the cooled steel plate. The cooled steel plate is tempered at 600℃ for 45min, and then air-cooled to room temperature to obtain a 30mm thick high-strength manganese-molybdenum-vanadium steel plate resistant to low temperature impact.

[0066] Comparative Example 8 Comparative Example 8 is the same as Example 1, except that the Ti content is lower, resulting in a Ti / N ratio of 2.6. Details are as follows: A low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate is made from the following raw materials by weight percentage: C 0.11%, Si 0.26%, Mn 1.55%, Mo 0.24%, V 0.09%, Ti 0.0117%, B 0.0018%, N 0.0045%, Al 0.02%, Ca 0.002%, P 0.006%, S 0.0018%, with the balance being Fe and unavoidable impurities; wherein, Ti / N=2.6, Mo / V=2.67, Ca / S=1.11.

[0067] A method for producing a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate includes the following steps: (1) Smelting and refining: Raw materials are prepared according to weight percentage, and molten iron is added to the converter for top and bottom blowing smelting. The carbon content at the end of the converter is controlled to be 0.045%, the phosphorus content at the end of the converter is 0.006%, and the tapping temperature is 1640℃. Slag-blocking tapping is adopted in the tapping process. When 1 / 3 of the steel is tapped, silicon manganese alloy, ferrosilicon and aluminum particles are added for preliminary deoxidation and basic alloying to obtain molten steel. Molten steel was transferred to an LF refining furnace and heated to 1590℃. 1% (by weight of the molten steel) of a BaO-MgO pre-melted composite slag-forming agent (prepared in Preparation Example 1) was added. During the LF refining process, the total FeO and MnO content in the slag was controlled at 0.8%, the white slag retention time was 22 min, and the total LF refining time was 35 min. In the LF refining stage, FeMo60, FeV50, FeTi70, and FeB20 were used to adjust Mo, V, Ti, and B to their target contents, respectively, to obtain refined molten steel. (2) Vacuum degassing and calcium treatment in VD furnace: The refined molten steel was transferred to a VD furnace and kept under a vacuum of 45 Pa for 16 min. During the vacuum treatment, the bottom blowing argon flow rate was 32 NL / min. After the vacuum was broken by VD, the temperature of the molten steel was controlled at 1575℃. Calcium treatment was performed using silicon-calcium alloy wire with a diameter of 13 mm. The wire feeding speed was 220 m / min, and the calcium treatment time was 3 min. The weight percentage of each component in the silicon-calcium alloy wire was as follows: Ca 30.2%, Si 59.1%, Al 0.8%, P 0.018%, S 0.012%, with the remainder being Fe and unavoidable impurities. The amount of silicon-calcium alloy wire added was 0.85 kg / t steel. After calcium treatment, the molten steel was soft-blown with argon at a flow rate of 20 NL / min for 12 min. After the VD treatment, the total oxygen content TO of the molten steel was 0.0016%, and the hydrogen content H was 0.00015%, resulting in degassed molten steel. (3) Continuous casting and dynamic light reduction: Argon gas protection is used for casting. The degassed molten steel is cast into a 100mm thick billet. The superheat of the molten steel in the tundish is controlled at 20℃ and the casting speed is controlled at 1m / min. The secondary cooling zone is cooled by gas-water atomization with a specific water volume of 0.55L / kg. At the end of the secondary cooling zone of the continuous casting machine, in the range where the solid fraction of the billet reaches 0.4-0.7, a light reduction of 4.8mm is applied. The reduction is distributed to 4 roll sections. The reduction of the 4 roll sections is 1mm, 1.2mm, 1.3mm and 1.3mm respectively to obtain the billet. (4) Step temperature uniform heating: The steel billet is loaded into the heating furnace, first heated to 1150℃ and held for 1.2h, then heated to 1220℃ and held for 0.8h, and finally cooled to 1180℃ for uniform heating for 0.8h before being taken out of the furnace to obtain the heated steel billet; (5) Rolling and heat treatment: The initial rolling temperature is controlled at 1120℃, the final rolling temperature is 830℃, and the total reduction rate is 70%. The heated steel billet is rolled to a thickness of 30mm in 6 passes to obtain the rolled steel plate. The rolled steel plate is cooled to 350℃ at a cooling rate of 32℃ / s, and then air-cooled to room temperature to obtain the cooled steel plate. The cooled steel plate is tempered at 600℃ for 45min, and then air-cooled to room temperature to obtain a 30mm thick high-strength manganese-molybdenum-vanadium steel plate resistant to low temperature impact.

[0068] The comprehensive performance of the low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plates prepared in Examples 1-3 and Comparative Examples 1-8 of this invention was tested respectively.

[0069] 1. Tensile property testing: The test was conducted according to GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test at room temperature" to determine the yield strength, tensile strength, and elongation after fracture. Tensile specimens were taken from the steel plate at 1 / 4 thickness along the rolling direction, with 3 specimens tested in each group, and the average value was taken.

[0070] 2. Low-temperature impact test: According to GB / T 229-2020 "Charpy impact test method for metallic materials", a 10mm×10mm×55mm V-notch standard specimen was prepared at 1 / 4 thickness of the steel plate along the rolling direction. After being kept at -40℃ in a low-temperature chamber, the pendulum impact test was carried out, and the absorbed impact energy was recorded. Three specimens were tested in each group, and the average value of the results was taken.

[0071] 3. Reduction of area in the thickness direction (Z-direction): The test was conducted according to GB / T 5313-2023 "Steel plates with properties in the thickness direction". Cylindrical tensile specimens were cut in the thickness direction of the steel plate, and the ability of the steel plate to resist lamellar tearing was evaluated by the percentage reduction of the cross-section after fracture (the greater the Z-direction reduction, the stronger the tear resistance). Three specimens were tested in each group, and the average value of the results was taken.

[0072] 4. Rating of non-metallic inclusions: Conventional optical microscopy tests were conducted according to GB / T 10561-2023 "Standard Rating Chart Microscopic Examination Method for Determination of Non-metallic Inclusion Content in Steel". The highest rating of inclusions in categories A, B, C and D was recorded respectively. Three samples were tested in each group, and the average value of the results was taken.

[0073] The test results are shown in Table 1: Table 1: As shown in Table 1, the low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plates prepared in Examples 1-3 of this invention all exhibit excellent comprehensive performance. Their yield strength is ≥900MPa, tensile strength is ≥1050MPa, elongation after fracture is ≥15%, Charpy V-notch impact energy at -40℃ is ≥100J, Z-direction reduction of area is ≥35%, and the highest rating of non-metallic inclusions of categories A, B, C and D is no higher than 0.5. Their comprehensive performance is far superior to that of comparative examples 1-8.

[0074] As shown in Example 1 and Comparative Examples 1-2, the use of a BaO-MgO pre-melted composite modified slag-forming agent resulted in improved -40℃ impact resistance and Z-direction reduction of area in the steel plate, while reducing the B and C inclusion ratings. This indicates that the combined effect of BaO and MgO enhances the adsorption, melting, and modification capabilities of the refining slag for alumina and silicate inclusions, thereby improving low-temperature impact toughness and thickness-direction properties.

[0075] As shown in Example 1 and Comparative Example 3, under the same conditions, after calcium treatment of silicon-calcium alloy wire with VD, the -40℃ impact resistance and Z-direction reduction of area of ​​the steel plate are significantly improved, and the inclusion ratings of Class A and Class B are significantly reduced. This indicates that calcium treatment is beneficial for converting residual high-melting-point Al2O3 inclusions into more stable calcium aluminate inclusions and reducing the adverse effects of long strip-shaped sulfides on performance.

[0076] As can be seen from Example 1 and Comparative Example 4, after implementing dynamic light pressing at the end of continuous casting solidification, the -40℃ impact resistance and Z-direction reduction of area of ​​the steel plate are significantly improved, indicating that dynamic light pressing is beneficial to reducing center segregation and center porosity, thereby improving the thickness direction performance and enhancing the low-temperature impact performance.

[0077] As can be seen from Example 1 and Comparative Example 5, after step-temperature homogenization heat treatment, the -40℃ impact resistance and Z-direction reduction of area of ​​the steel plate are significantly improved, indicating that step-temperature homogenization heat treatment can promote the diffusion of segregated elements while inhibiting excessive coarsening of austenite grains, thereby improving the strength and toughness combination of the steel plate.

[0078] As can be seen from Example 1 and Comparative Example 6, under basically the same conditions, the addition of Mo significantly improved the yield strength, tensile strength and -40℃ impact energy of the steel plate, indicating that Mo is beneficial to improving the hardenability of thick steel plates and improving the strength level and low-temperature toughness matching after tempering.

[0079] As shown in Example 1 and Comparative Examples 7-8, when the Ti / N ratio is controlled within the range of 3.45-3.95, the steel plate can achieve a better balance between strength and toughness. When the Ti / N ratio is too high or too low, the impact energy at -40℃ will decrease, and the yield strength will also decrease. This indicates that an excessively high Ti / N ratio easily leads to the formation of coarse TiN particles, while an excessively low Ti / N ratio is not conducive to the effective fixation of N and weakens the effective role of B. Both are detrimental to the coordination of strength and low-temperature impact toughness.

[0080] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel sheet, characterized by, It is made from the following raw materials in weight percentage: C 0.08-0.14%, Si 0.18-0.35%, Mn 1.3-1.75%, Mo 0.18-0.32%, V 0.06-0.12%, Ti 0.013-0.019%, B 0.001-0.0025%, N 0.0036-0.0048%, Al 0.012-0.028%, Ca 0.001-0.003%, P≤0.008%, S 0.0005-0.0025%, with the balance being Fe and unavoidable impurities.

2. The low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate according to claim 1, characterized in that, The mass ratio of Ti to N in the raw material components satisfies: 3.45 ≤ Ti / N ≤ 3.

95.

3. The low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate according to claim 1, characterized in that, The mass ratio of Mo and V in the raw material components satisfies: 2.2 ≤ Mo / V ≤ 3.

4. The low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate according to claim 1, characterized in that, The mass ratio of Ca to S in the raw material components satisfies: 0.8 ≤ Ca / S ≤ 2.

5. A method for producing a low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Smelting and refining: Raw materials are prepared according to weight percentage. The molten iron is smelted in a converter and then tapped into steel. The molten steel is transferred to the LF refining furnace. During the LF refining period, a pre-melted composite slag-forming agent containing BaO-MgO is added to form white slag, desulfurize, deoxidize and adsorb inclusions. In the LF refining stage, ferromolybdenum, ferrovanadium, ferrotitanium and ferroboron alloys are added to adjust Mo, V, Ti and B to the target range to obtain refined molten steel. (2) VD vacuum degassing and calcium treatment: The refined molten steel is subjected to VD vacuum degassing. After the vacuum is broken by VD, the silicon-calcium alloy wire is subjected to calcium treatment. After the calcium treatment, soft argon blowing is performed to obtain calcium-treated molten steel. (3) Continuous casting and dynamic light reduction: The calcium-treated molten steel is continuously cast into a billet, and a dynamic light reduction process is implemented at the end of the billet solidification period to obtain the billet. (4) Stepped temperature uniform heating: The steel billet is subjected to stepped temperature uniform heating treatment; (5) Rolling and heat treatment: The heated steel billet is subjected to controlled rolling, controlled cooling and tempering to obtain a high-strength manganese-molybdenum-vanadium steel plate resistant to low-temperature impact.

6. The method for producing low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate according to claim 5, characterized in that, In step (1), the mass percentage of the components of the BaO-MgO pre-melted composite modified slag-forming agent is: BaO 10-14%, Al2O3 28-34%, MgO 3-6%, SiO2 1-3.5%, and the balance is CaO.

7. The method for producing low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate according to claim 6, characterized in that, The BaO-MgO pre-melted composite modified slagging agent is prepared by the following method: Using lime, industrial alumina, quartz sand, lightly calcined magnesia, and barium carbonate as raw materials, the raw materials are calculated and proportioned according to the target oxide composition. After drying the raw materials at 180-220℃ for 1-3 hours, they are mixed evenly and melted at 1450-1500℃ for 30-45 minutes. Then, they are water-quenched and crushed, and sieved to obtain pre-melted particles with a particle size of 5-30 mm. These particles are then dried at 160-200℃ until the moisture content is ≤0.3%, thus obtaining the BaO-MgO pre-melted composite modified slagging agent.

8. The method for producing low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate according to claim 5, characterized in that, In step (2), after the vacuum is broken by VD, the temperature of the molten steel is 1565-1585℃. Calcium treatment is performed using silicon-calcium alloy wire with a diameter of 13mm. The wire feeding speed is 180-260m / min, and the calcium treatment time is 2-4min. The weight percentage content of each component in the silicon-calcium alloy wire is as follows: Ca 28-32%, Si 55-65%, Al≤1.5%, P≤0.04%, S≤0.04%, with the balance being Fe and unavoidable impurities. The amount of silicon-calcium alloy wire added is 0.6-1.1kg / t steel. After calcium treatment, the steel is soft-blown with argon gas at a flow rate of 15-25NL / min for 8-15min.

9. The method for producing low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate according to claim 5, characterized in that, In step (3), the operation of the dynamic light reduction process is as follows: at the end of the secondary cooling zone of the continuous casting machine, within the range where the solid fraction of the billet center reaches 0.4-0.7, a light reduction of 3.5-6 mm is applied.

10. The method for producing low-temperature impact-resistant manganese-molybdenum-vanadium high-strength steel plate according to claim 5, characterized in that, In step (4), the specific operation of the stepped temperature change heating is as follows: first, heat the billet to 1140-1160℃ and hold for 1-1.5h, then heat it to 1210-1230℃ and hold for 0.5-1h, and finally cool it down to 1170-1190℃ for 0.5-1h before taking it out of the furnace.

Images