Ultrahigh-strength low-temperature steel plate with excellent firework performance and manufacturing method

Abstract

The invention provides an ultrahigh-strength low-temperature steel plate with excellent firework performance and a manufacturing method thereof. The steel plate comprises the following components in percentage by weight: 0.080%-0.200% of C, 0.70%-1.30% of Si, 1.60%-2.10% of Mn, less than or equal to 0.008% of P, less than or equal to 0.005% of S, 0.080%-0.230% of V, 0.0220%-0.0280% of N, 0.70%-1.05% of Cu, 1.30%-1.70% of Ni, 0.40%-0.60% of Mo, 0.020%-0.040% of Ti, 0.040%-0.060% of Als, 0.0300%-0.0360% of La and the balance of Fe. And the balance of Fe and inevitable impurities. The manufacturing method comprises the steps of smelting, continuous casting, reheating, rolling, accelerated cooling and tempering. According to the steel plate produced by the method, the steel plate with excellent comprehensive mechanical properties and fire work performance is finally obtained, the yield strength of the steel plate after fire work is larger than or equal to 560 MPa, the tensile strength is 660-710 MPa, the percentage elongation after fracture is larger than or equal to 21.5%, and the impact absorption energy at the temperature of-80 DEG C is larger than or equal to 190 J.

Description

Technical Field

[0001] The invention belongs to the field of metal materials, and in particular relates to an ultra-high-strength low-temperature steel plate with excellent pyrotechnic performance and a manufacturing method thereof. Background Art

[0002] The hull structure is different from other structures. Due to the huge size of the hull, the large number of parts, the complex structure and high rigidity, the various processed longitudinal and transverse components and curved components in the hull intersect and link with each other, which inevitably produces bending deformation, angular deformation, local bulge wave deformation and twisting deformation during the construction process. Therefore, in order to obtain the curved shape of the hull construction design or to avoid the deformation of the steel plate that seriously affects the assembly quality of the hull and the linear smoothness of the hull, pyrotechnics must be used to perform corresponding pyrotechnic forming and water-fire bending plate and other deformation corrections during ship construction.

[0003] Water-fire bending is a process that uses flames to locally heat steel plates and then uses water to cool them to bend them. Current research on the pyrotechnic properties of ship plates shows that despite strict requirements for the pyrotechnic process of ship plates during ship construction, it is still difficult to guarantee the pyrotechnic performance. At present, the production of ship plates also pays more attention to component design, rolling and welding processes, while less attention is paid to water-fire bending and its performance changes during subsequent processing.

[0004] The patent document "A low-temperature steel plate for ships with excellent pyrotechnic performance and its manufacturing method" (application number: 201910863007.9) discloses a low-temperature steel for ships with excellent pyrotechnic performance, whose main chemical components are C 0.04%-0.08%, Si 0.15%-0.25%, Mn 0.80%-1.80%, Als0.045%-0.070%, N≤0.0040%, Ti 0.005%-0.020%, and the rest are Fe and unavoidable impurities. Its process includes heating of ingot, two-stage rolling and controlled cooling. The steel plate has excellent comprehensive performance and excellent pyrotechnic performance. However, its tensile strength is only 510MPa, which is difficult to meet the needs of large ship construction.

[0005] The patent document "A thick steel plate with high crack arrest performance and its manufacturing method" (application number: 202110416833.6) discloses a thick steel plate with high crack arrest performance, whose chemical composition is C0.04%-0.15%, Si 0.10%-0.30%, Mn 1.00%-3.50%, Cr 0.01%-0.80%, Ni0.10%-2.50%, Mo0.001%-0.80%, Cu 0.001%-0.60%, Al 0.01%-0.06%, Nb0.01%-0.06%, Ti 0.01%-0.06%, Ca 0.001-0.0045%, the rest is Fe and unavoidable impurities, its tensile strength is 570-720-MPa, and the Charpy impact energy at -40℃ is ≥100J; its disadvantage is that the addition of a relatively high Mn element can easily cause core segregation of the steel plate, affecting its comprehensive mechanical properties.

[0006] The patent document "A high-quality steel plate for low-temperature oil storage tanks and its production method" (application number: 202310447564.9) discloses a steel plate for low-temperature oil storage tanks, whose chemical composition is C 0.05%-0.07%, Si 0.10%-0.30%, Mn 1.45%-1.55%, Cr 0.20%-0.25%, V 0.035%-0.040%, Ni 0.15%-0.20%, Ti 0.025%-0.030%, Nb 0.020%-0.025%, Alt≤0.010%, B 0.0010%-0.0015%, and the remainder is Fe and unavoidable impurities. The production method of the steel plate includes smelting, rolling, quenching + tempering and other processes. The process is complicated, and the steel plate only has an impact toughness of -20°C, which is far from meeting the use requirements. At the same time, the steel plate has not been evaluated for its pyrotechnic performance.

[0007] To sum up, the current production of shipbuilding steel mainly has the following problems.

[0008] 1) Quenching treatment is required, and the process is complicated, which increases the production cost of the steel plate.

[0009] 2) The strength and toughness of steel plates are relatively low and cannot meet the needs of shipbuilding.

[0010] 3) The pyrotechnic performance of steel plates is relatively low and cannot meet the technological requirements of shipbuilding. Summary of the invention

[0011] The purpose of the present invention is to overcome the above-mentioned problems and shortcomings and to provide an ultra-high strength low-temperature steel plate and a manufacturing method with excellent comprehensive mechanical properties. The yield strength of the steel plate after pyrolysis is ≥560MPa, the tensile strength is 660-710MPa, the elongation after fracture is ≥21.5%, and the impact absorption energy at -80℃ is ≥190J.

[0012] The object of the invention is achieved in this way:

[0013] The invention discloses an ultra-high strength low-temperature steel plate with excellent pyrotechnic performance. The components of the steel plate are as follows by weight percentage: C: 0.080%-0.200%, Si: 0.70%-1.30%, Mn: 1.60%-2.10%, P≤0.008%, S≤0.005%, V: 0.080%-0.230%, N: 0.0220%-0.0280%, Cu: 0.70%-1.05%, Ni: 1.30%-1.70%, Mo: 0.40%-0.60%, Ti: 0.020%-0.040%, Als: 0.040%-0.060%, La: 0.0300%-0.0360%; the balance is Fe and unavoidable impurities.

[0014] Furthermore, Ni / Mo in the steel plate is 2.5 to 3.6.

[0015] The metallographic structure of the steel plate is a small amount of ferrite + tempered bainite structure, wherein the ferrite content is 10.0-15.0%, the average grain size is ≤10 μm, and the average precipitate phase size is ≤20 nm.

[0016] The steel plate has a yield strength of ≥570MPa, a tensile strength of 670-720MPa, an elongation after fracture of ≥22.0%, and an impact absorption energy of -80°C of ≥260J; the yield strength of the steel plate after pyrolysis is ≥560MPa, a tensile strength of 660-710MPa, an elongation after fracture of ≥21.5%, and an impact absorption energy of -80°C of ≥190J.

[0017] The reasons for the composition design of the present invention are as follows:

[0018] C: An important strengthening element in steel. In the technical solution of the present invention, it is the main element for controlling the composition of the steel plate, optimizing the precipitation of microalloy elements in the steel, and ensuring the strength and hardness of the steel plate after rolling and pyrotechnic bending. When the content is low, the amount of carbide generated will be reduced, affecting the effect of grain refinement during rolling and pyrotechnic treatment. When the content is high, the cementite content in the steel increases, which is unfavorable to the low-temperature toughness and welding performance of the steel plate. Therefore, considering the cost, performance and other factors, the present invention controls C in the range of 0.080% to 0.200%.

[0019] Si: It can improve the strength and hardness of steel and play a role in deoxidation during the steelmaking process. When the content is too high, it will cause the tough-brittle transition temperature of steel to rise and reduce the low-temperature toughness of the steel plate, thus having an adverse effect on the comprehensive performance of the steel plate after pyrotechnics. Taking into account factors such as cost and performance, the present invention controls the range of Si to be 0.70% to 1.30%.

[0020] Mn: an element that expands the austenite phase region, forms a substitutional solid solution in steel, can be dissolved in a large amount in the Fe matrix, improves the strength of the steel through solid solution strengthening, and has a positive effect on grain refinement; it can delay the transformation of ferrite and pearlite in steel, greatly increase the hardenability of steel, reduce the toughness-brittle transition temperature of steel, and change the impact toughness. However, if the Mn content is too high, it is easy to form segregation in the steel, which has an adverse effect on the plasticity and toughness of the steel. Taking all factors into consideration, the range of Mn controlled by the present invention is 1.60% to 2.10%.

[0021] V: An important strengthening and toughening element of the present invention, a strong carbon and nitride forming element, a strong carbide and nitride forming element, has a strong affinity with nitrogen and carbon, and can form extremely stable carbonitrides with them. The strength of steel is improved by fine grain strengthening, precipitation strengthening and solid solution strengthening in steel. As the V content increases, the tough-to-brittle transition temperature of steel decreases. However, when the content is too high, the tough-to-brittle transition temperature increases instead. Vanadium carbonitrides can precipitate at a lower temperature to hinder dislocation movement, play a strengthening and toughening role, and have a significant effect on improving the comprehensive mechanical properties of steel plates after pyrotechnic treatment. Taking all factors into consideration, the present invention controls the range of V to be 0.080% to 0.230%.

[0022] N: Another important toughening element of the present invention. The addition of N element is conducive to promoting the formation of a large amount of V (CN) in the steel, thereby refining its grains and improving the plasticity and toughness of the steel. Nitrogen-containing steel not only eliminates the cost increase caused by degassing and refining and denitrification in the steelmaking process, but also the nitrogen addition in the steel can give full play to the role of micro-alloying elements, saving the amount of alloying elements, thereby greatly reducing production costs. The addition of N can optimize the precipitation of precipitated phases during pyrotechnic treatment of steel, thereby improving its comprehensive mechanical properties. Taking into account the performance and cost, the present invention controls the range of N to be 0.0220% to 0.0280%.

[0023] Cu: It can improve the stability of austenite in steel, increase the hardenability of steel, and improve the strength, plasticity and low-temperature toughness of steel when added in appropriate amounts. During low-temperature treatment, ε-Cu precipitation can be produced, thereby improving the strength of steel. However, when the content is too high, the hot brittleness of steel deteriorates and hot cracks are easily generated. The present invention controls the range of Cu to be 0.70% to 1.05%.

[0024] Ni: has no adverse effect on the hardenability and toughness of the welding heat affected zone of steel, and can improve the plasticity and low-temperature toughness of steel. When combined with Mo, it has a more detailed fine grain effect. In addition, the addition of Ni can also reduce the tendency of thermal cracking when the Cu content is high. Considering factors such as cost and performance, the present invention controls the range of Ni to be 1.30% to 1.70%.

[0025] Mo: improves the hardenability of steel, and the effect is more obvious when used in combination with Ni. It can enable the steel to obtain bainite structure within a wider cooling rate, refine the grains, and form fine carbides in the steel, which can effectively improve the strength and toughness of the steel. Taking into account factors such as steel cost and performance, the present invention controls Mo in the range of 0.40% to 0.60%, and Ni / Mo=2.5 to 3.6.

[0026] Ti: It can produce a strong precipitation strengthening effect, improve the strength of steel, and prevent austenite recrystallization; at the same time, it can produce a grain refinement effect and improve the yield strength of steel. The carbon and nitride of Ti have a high dissolution temperature, which will prevent the growth of austenite grains when heated, thereby refining the grain size of the steel plate, improving its strength and toughness, and promoting the comprehensive mechanical properties of the steel plate after pyrotechnic treatment. Taking all factors into consideration, the present invention controls the range of Ti to be 0.020% to 0.040%.

[0027] Al: A strong deoxidizer in steel. A small amount of Al can generate highly fine and ultra-micro oxides, which has a beneficial effect on improving the purity of steel. The purpose of adding Al in the present invention is to ensure that the molten steel is fully deoxidized and to create conditions for the subsequent addition of La and other elements. The present invention controls the range of Als to be 0.040% to 0.060%.

[0028] La: rare metal element, has good deoxidation and desulfurization effects, improves the fluidity of steel, reduces non-metallic inclusions, makes the steel structure dense and pure, improves the anisotropic properties of steel, has a beneficial effect on improving the impact toughness of steel, especially low-temperature impact toughness, and can effectively prevent the growth of steel plate grains during pyrotechnic treatment, thereby improving its comprehensive mechanical properties. The total amount of La added in the present invention is controlled to be 0.0300% to 0.0360%.

[0029] The second technical solution of the present invention is to provide a method for manufacturing an ultra-high strength low temperature steel plate with excellent pyrotechnic performance, including smelting, continuous casting, reheating, rolling, accelerated cooling, and tempering;

[0030] Smelting: Smelting the steel according to the above composition, including converter smelting, refining, and RH treatment;

[0031] a) adjusting the contents of elements such as C, Si, Mn, P, S, etc. during converter smelting to be within the scope of the present invention, and adding other alloy components for smelting as required;

[0032] b) refining the molten steel and adjusting the contents of other alloying elements within the range of the present invention;

[0033] c) subjecting the refined molten steel to RH treatment for 40 to 60 minutes, blowing nitrogen throughout the RH treatment at a pressure of 570 to 610 Pa, ensuring that the final nitrogen content of the steel is within the range of the present invention, and controlling [H]≤2.0ppm and [O]≤10ppm in the steel;

[0034] d) Add La element 10 minutes before the end of RH treatment;

[0035] Continuous casting: The obtained molten steel is continuously cast to obtain the required ingot. The tundish adopts low superheat, the superheat is ≤25℃, the casting is protected throughout the process, the billet drawing speed is controlled to be 1.0-1.5m / min, the secondary cooling water ratio is 0.15-0.35m3 / t, electromagnetic stirring is adopted during the continuous casting process, the stirring current is 400-500A, and the light pressure reduction process is adopted at the end of the continuous casting, and the pressure reduction is 5.0-10.0mm; low superheat is adopted in the continuous casting process to reduce the center segregation of the ingot, and electromagnetic stirring and light pressure are used to further control the segregation of the ingot;

[0036] In order to control the grain size of the continuous casting billet, the continuous casting billet is stacked and slowly cooled. The stacking starting temperature is 680-730℃ and the slow cooling time is ≥36h.

[0037] Reheating: After that, the ingot is reheated to 1100℃~1250℃, the holding time is 0.5~1.5h, and the total furnace time is 3.0~5.0h;

[0038] Rolling: The ingot is rolled into hot-rolled steel plate in two stages. In the first stage, in order to fully break the columnar crystals of the continuous casting ingot and prepare for the subsequent grain refinement, the high-temperature rapid rolling + large reduction method is adopted. The roller speed is controlled at 1.5-2.5m / s, and the average reduction of the first three passes is controlled to be 50-60mm. The final rolling temperature is above 1050℃, and the thickness of the warm billet is (2.5-3.5)t, where t is the thickness of the final product; the second stage rolling temperature is 870-920℃, and the final rolling temperature is 800-850℃;

[0039] Accelerated cooling: In order to maintain fine grains after rolling and prevent grain growth, the steel plate is cooled at an accelerated rate of 700-800°C, with a cooling rate of 8.0-25.0°C / s and a red-return temperature of ≤200°C.

[0040] Tempering: The cooled steel plate is tempered at a temperature of 600-700°C and a furnace time of 5.0-7.0 min / mm;

[0041] The rolling process adopts two-stage controlled rolling. The first stage adopts high-temperature rapid rolling + high pressure reduction process, and the second stage adopts a rapid rolling process with a high final rolling temperature to obtain refined grains, in preparation for subsequent rapid cooling after rolling. The rolled steel plate adopts an accelerated cooling process with a high opening cooling temperature + a high-temperature tempering process to control the internal stress and precipitation phase distribution of the final steel plate, and no quenching treatment is required.

[0042] The beneficial effects of the present invention are:

[0043] (1) The present invention adopts a low-carbon chemical composition system to improve the low-temperature toughness of steel, and adds VN and other grain-refining elements, while promoting the formation of ferrite structure in steel, adding La element, modifying molten steel, and improving the purity of steel; the continuous casting process adopts low superheat to reduce the center segregation of the ingot, and electromagnetic stirring and light pressure are used to further control the segregation of the ingot; the rolling process adopts two-stage controlled rolling, the first stage of rolling adopts a high-temperature rapid rolling + high pressure reduction process, and the second stage adopts a high final rolling temperature rapid rolling process to obtain refined grains, in preparation for subsequent rapid cooling after rolling; the rolled steel plate adopts a high opening cooling temperature accelerated cooling process + high-temperature tempering process to control the internal stress and precipitation phase distribution of the final steel plate, and no quenching treatment is required.

[0044] (2) The metallographic structure of the steel plate is a small amount of ferrite + tempered bainite structure, wherein the ferrite content is 10.0-15.0%, the average grain size is ≤10μm, and the average size of the precipitated phase is ≤20nm. Finally, a steel plate with excellent comprehensive mechanical properties and pyrotechnic properties is obtained, with a yield strength of ≥570MPa, a tensile strength of 670-720MPa, an elongation after fracture of ≥22.0%, and an impact absorption energy of -80℃ of ≥260J; the yield strength of the steel plate after pyrotechnics is ≥560MPa, a tensile strength of 660-710MPa, an elongation after fracture of ≥21.5%, and an impact absorption energy of -80℃ of ≥190J. DETAILED DESCRIPTION

[0045] The present invention will be further described below by way of examples.

[0046] The embodiment of the present invention performs smelting, continuous casting, reheating, rolling, accelerated cooling and tempering according to the component ratio of the technical solution;

[0047] Continuous casting: The tundish adopts low superheat, superheat ≤ 25℃, full protection casting, and the billet drawing speed is controlled at 1.0-1.5m / min. The water volume of secondary cooling water is 0.15-0.35m3 / t. Electromagnetic stirring is used during continuous casting, and the stirring current is 400-500A. At the end of continuous casting, a light reduction process is used, and the reduction is 5.0-10.0mm.

[0048] Rolling: The ingot is rolled into hot-rolled steel plate in two stages. The first stage is carried out by high-temperature rapid rolling + large reduction. The roller speed is controlled at 1.5-2.5 m / s, and the average reduction of the first three passes is controlled to be 50-60 mm. The final rolling temperature is above 1050°C, and the thickness of the warm billet is (2.5-3.5) t, where t is the thickness of the final product. The second stage has a starting rolling temperature of 870-920°C and a final rolling temperature of 800-850°C.

[0049] Accelerated cooling: In order to maintain fine grains after rolling and prevent grain growth, the steel plate is cooled at an accelerated rate of 700-800°C, with a cooling rate of 8.0-25.0°C / s and a red-return temperature of ≤200°C.

[0050] Tempering: The cooled steel plate is tempered at a temperature of 600-700°C and a furnace time of 5.0-7.0 min / mm.

[0051] Further; reheating: the ingot is reheated to 1100℃~1250℃, the holding time is 0.5~1.5h, and the total time in the furnace is 3.0~5.0h.

[0052] Furthermore, after continuous casting and before reheating, the continuously cast billets are stacked and slowly cooled, the stacking starting temperature is 680-730°C, and the slow cooling time is ≥36h.

[0053] The composition of the steel of the embodiment of the present invention is shown in Table 1. The main process parameters of smelting and continuous casting of the steel of the embodiment of the present invention are shown in Table 2. The main process parameters of heating and rolling of the steel of the embodiment of the present invention are shown in Table 3-Table 4. The main heat treatment process parameters of cooling and tempering of the steel of the embodiment of the present invention are shown in Table 5. The organizational characteristics of the steel of the embodiment of the present invention are shown in Table 6, the mechanical properties of the steel of the present invention are shown in Table 7, and the pyrotechnic properties of the steel of the present invention are shown in Table 8.

[0054] Table 1 Composition of steel according to the present invention (wt%)

[0055]

[0056] Table 2 Main process parameters of steel smelting and continuous casting in the embodiment of the present invention

[0057]

[0058] Table 3 Heating process of steel in the embodiment of the present invention

[0059] Example Heating temperature / ℃ Insulation time / h Total furnace time / h 1 1109 0.9 3.8 2 1118 0.8 3.9 3 1241 1.1 4.1 4 1233 1.3 4.6 5 1127 1.1 4.4 6 1222 0.6 3.2 7 1139 0.7 3.4 8 1214 0.9 3.6 9 1158 1.2 4.8 10 1203 1.3 4.9

[0060] Table 4 Main process parameters of steel rolling in the embodiment of the present invention

[0061]

[0062] Table 5 Main process parameters of cooling and tempering in the embodiment of the present invention

[0063]

[0064] Table 6 Microstructure characteristics of the steel according to the present invention

[0065] Example Ferrite content Average grain size / μm Precipitation phase size / nm 1 13.2 9.2 19.8 2 12.8 10.4 17.9 3 14.9 12.6 18.8 4 11.3 11.3 18.4 5 14.2 10.8 17.4 6 13.6 12.4 16.8 7 11.7 11.7 17.2 8 10.9 10.2 15.9 9 13.8 9.8 19.4 10 10.1 11.6 18.6

[0066] Table 7 Steel properties of the present invention

[0067]

[0068] Table 8 Explosive properties of the steel of the present invention

[0069]

[0070] The metallographic structure of the steel plate produced by the present invention is a small amount of ferrite + tempered bainite structure, wherein the ferrite content is 10.0-15.0%, the average grain size is ≤10μm, and the average size of the precipitated phase is ≤20nm. Finally, a steel plate with excellent comprehensive mechanical properties and pyrotechnic properties is obtained, with a yield strength of ≥570MPa, a tensile strength of 670-720MPa, an elongation after fracture of ≥22.0%, and an impact absorption energy of ≥260J at -80℃; the yield strength of the steel plate after pyrotechnics is ≥560MPa, a tensile strength of 660-710MPa, an elongation after fracture of ≥21.5%, and an impact absorption energy of ≥190J at -80℃.

[0071] In order to describe the present invention, the present invention is appropriately and fully illustrated by the examples in the above. The above implementation modes are only used to illustrate the present invention, but not to limit the present invention. Ordinary technicians in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made should be included in the protection scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. An ultra-high strength low temperature steel plate with excellent pyrotechnic performance, characterized in that: The components of the steel plate are as follows by weight percentage: C: 0.080%-0.200%, Si: 0.70%-1.30%, Mn: 1.60%-2.10%, P≤0.008%, S≤0.005%, V: 0.080%-0.230%, N: 0.0220%-0.0280%, Cu: 0.70%-1.05%, Ni: 1.30%-1.70%, Mo: 0.40%-0.60%, Ti: 0.020%-0.040%, Al: 0.040%-0.060%, La: 0.0300%-0.0360%; the balance is Fe and unavoidable impurities.

2. The ultra-high strength and low temperature steel plate with excellent pyrotechnic performance according to claim 1, characterized in that: In the steel plate, Ni / Mo=2.5-3.

6.

3. The ultra-high strength and low temperature steel plate with excellent pyrotechnic performance according to claim 1, characterized in that: The metallographic structure of the steel plate is a small amount of ferrite + tempered bainite structure, wherein the ferrite content is 10.0-15.0%, the average grain size is ≤10 μm, and the average precipitate phase size is ≤20 nm.

4. The ultra-high strength and low temperature steel plate with excellent pyrotechnic performance according to claim 1, characterized in that: The steel plate has a yield strength of ≥570MPa, a tensile strength of 670-720MPa, an elongation after fracture of ≥22.0%, and an impact absorption energy of -80°C of ≥260J; the yield strength of the steel plate after pyrolysis is ≥560MPa, a tensile strength of 660-710MPa, an elongation after fracture of ≥21.5%, and an impact absorption energy of -80°C of ≥190J.

5. A method for manufacturing an ultra-high strength low temperature steel plate with excellent pyrotechnic performance according to any one of claims 1 to 4, comprising smelting, continuous casting, reheating, rolling, accelerated cooling, and tempering; characterized in that: Continuous casting: The tundish adopts low superheat, superheat ≤ 25℃, full protection casting, and the billet drawing speed is controlled at 1.0-1.5m / min. The water volume of secondary cooling water is 0.15-0.35m3 / t. Electromagnetic stirring is used during continuous casting, and the stirring current is 400-500A. At the end of continuous casting, a light reduction process is used, and the reduction is 5.0-10.0mm. Rolling: The ingot is rolled into hot-rolled steel plate in two stages. The first stage is carried out by high-temperature rapid rolling + large reduction. The roller speed is controlled at 1.5-2.5 m / s, and the average reduction of the first three passes is controlled to be 50-60 mm. The final rolling temperature is above 1050°C, and the thickness of the warm billet is (2.5-3.5) t, where t is the thickness of the final product. The second stage has a starting rolling temperature of 870-920°C and a final rolling temperature of 800-850°C. Accelerated cooling: In order to maintain fine grains after rolling and prevent grain growth, the steel plate is cooled at an accelerated rate of 700-800°C, with a cooling rate of 8.0-25.0°C / s and a red-return temperature of ≤200°C. Tempering: The cooled steel plate is tempered at a temperature of 600-700°C and a furnace time of 5.0-7.0 min / mm.

6. The method for manufacturing an ultra-high strength low temperature steel plate with excellent pyrotechnic performance according to claim 5, characterized in that: Reheating: The ingot is reheated to 1100℃~1250℃, the holding time is 0.5~1.5h, and the total time in the furnace is 3.0~5.0h.

7. The method for manufacturing an ultra-high strength and low temperature steel plate with excellent pyrotechnic performance according to claim 6, characterized in that: After continuous casting and before reheating, the continuously cast billets are stacked and slowly cooled. The stacking starting temperature is 680-730°C and the slow cooling time is ≥36h.

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