Ingot high-Al-content high-strength low-temperature A633D steel plate and production method

Abstract

The invention discloses an ingot high-Al-content high-strength low-temperature A633D steel plate and a production method thereof. The A633D steel plate comprises the following chemical components in percentage by mass: 0.14 to 0.17 percent of C, 0.20 to 0.45 percent of Si, 1.45 to 1.60 percent of Mn, less than or equal to 0.012 percent of P, less than or equal to 0.003 percent of S, 0.25 to 0.50 percent of Alt and the balance of Fe and trace unavoidable impurities. The production method comprises the working procedures of smelting, die casting, heating, rolling, stacking and slow cooling and normalizing heat treatment. In the normalizing heat treatment process, heating must be sufficient, the normalizing temperature is 900-910 DEG C, and the heat preservation time is 1.8-2.1 min / mm; and after normalizing and discharging, water cooling is carried out for accelerating cooling, and the cooling speed is 0.8-2 DEG C / s. Tapping conditions are strictly controlled, a fine smelting process is adopted, ultrahigh-aluminum-content refined grains are adopted, and the internal quality of the steel plate is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metallurgy, and particularly relates to a high-Al-content high-strength low-temperature A633D steel plate and a production method thereof. BACKGROUND

[0002] A633D belongs to a low-alloy high-strength structural steel plate, and has relatively high comprehensive mechanical properties in a normalized state; and is used in the manufacturing fields of bridges, ships, vehicles, boilers, high-pressure containers, oil and gas pipelines, and large steel structures. In order to ensure good low-temperature impact performance at a low-alloy cost, the current market 60-110 mm normalized high-strength steel A633D steel adopts the addition of nickel elements and niobium elements to ensure the low-temperature impact performance of the steel plate, but the cost of nickel alloy and niobium alloy is relatively high. Al, as one of the elements for refining grains, is applied, but the content is generally below 0.1%.

[0003] Low-alloy high-strength structural steel (HSLA) is widely used in the fields of bridges, ships, vehicles, boilers, high-pressure containers, oil and gas pipelines, and large steel structures due to its excellent strength, toughness and welding performance. Among them, A633D steel, as a typical low-alloy high-strength steel, is usually used in a normalized state to meet the requirement of relatively high comprehensive mechanical properties, especially the good impact toughness in a low-temperature environment.

[0004] In order to ensure the low-temperature impact performance, the traditional A633D steel usually adopts the way of adding alloy elements such as nickel (Ni) and niobium (Nb). Ni element can significantly improve the low-temperature toughness of the steel and reduce the ductile-brittle transition temperature, but its cost is high, which increases the production cost of the steel. Nb element improves the strength and toughness of the steel through grain refinement and precipitation strengthening, but its price is also expensive, and the process control requirement in the smelting and rolling process is relatively high, which is easy to cause the performance fluctuation of the steel plate due to uneven precipitation or excessive addition. In addition, the addition of Ni and Nb may also have an adverse effect on the welding performance and increase the welding crack sensitivity.

[0005] Aluminum (Al) as a common deoxidizer and grain refinement element usually exists in the form of acid-soluble aluminum (Alt) in steel, and its content is generally controlled below 0.1%. The main functions of Al include: 1) deoxidation: Al combines with oxygen in the steel liquid to form Al2O3, reduces the oxide inclusions in the steel, and improves the purity of the steel. 2) grain refinement: Al combines with nitrogen to form AlN, which can act as a heterogeneous nucleation core in the steel liquid solidification and subsequent heat treatment process, promote grain refinement, and improve the strength and toughness of the steel. 3) inhibit grain growth: In the rolling and cooling process, AlN particles can pin the grain boundaries and dislocations, hinder the migration of grain boundaries, further refine the grains, and improve the comprehensive performance of the steel.

[0006] However, the Al content in the traditional A633D steel is low, and its grain refinement effect is limited, which cannot completely replace the role of Ni and Nb. Therefore, how to reduce the alloy cost while ensuring the low-temperature impact performance has become an important direction for the current research and development of A633D steel.

[0007] In addition, with the continuous improvement of engineering application requirements, the market demand for thicker specifications (such as 60-110 mm) A633D steel plates is increasing. However, the maximum thickness specified in the ASTM A633 / A633M standard is only 100 mm, and it is difficult to ensure the stability of the mechanical properties, especially the low-temperature impact toughness, of the steel plates beyond this range under the traditional composition and process conditions. Therefore, it is urgent to develop a new type of high-Al-content A633D steel to meet the performance requirements of thicker steel plates while reducing costs by optimizing the composition design and production process.

[0008] In summary, the existing A633D steel still has certain limitations in low-temperature toughness, cost control, and thick-gauge production. The present application successfully develops a low-cost, high-performance ingot-to-plate high-Al-content A633D steel by significantly increasing the Al content (0.25-0.50%) and optimizing the smelting, rolling, and heat treatment processes, providing a new solution for the production of thick-gauge low-temperature high-strength steel. SUMMARY

[0009] The present application discloses an ingot-to-plate high-Al-content high-strength low-temperature A633D steel plate and a production method. By adjusting the alloy element ratio, controlling rolling and normalizing heat treatment, the present application improves the microstructure of the steel plate, so that the steel plate has good low-temperature impact performance at-50℃, the steel plate has a Z25 level anti-laminated tearing capacity, and the market competitiveness is effectively enhanced.

[0010] To solve the above technical problems, the technical scheme adopted by the present application is as follows: an ingot-to-plate high-Al-content high-strength low-temperature A633D steel plate, characterized in that the chemical composition and mass percentage of the A633D steel plate are as follows: C: 0.14-0.17%, Si: 0.20-0.45%, Mn: 1.45-1.60%, P≤0.012%, S≤0.003%, Alt: 0.25-0.50%, and the balance is Fe and trace amounts of unavoidable impurities. The Alt content is 0.25-0.50%, which increases the precipitation of the second phase, replaces Nb and Ni, reduces the cost, and has stable performance.

[0011] The steel plate has a metallographic structure of ferrite + pearlite + a small amount of bainite, wherein the bainite accounts for 10-23%.

[0012] The steel plate of this invention has a thickness of 60-110mm, with some thicknesses exceeding the 100mm thickness range specified in the ASTM A633 / A633M standard. The flaw detection meets the acceptance level Level I of GB / T2970-2016.

[0013] The steel plate described in this invention has the following properties: yield strength ≥339MPa, tensile strength 490~550MPa, elongation ≥24%, average longitudinal impact energy at -50℃ ≥80J, and reduction of area ≥25% for thick tensile sections.

[0014] Another objective of this invention is to provide a method for producing high-Al content, high-strength, low-temperature A633D steel plates from ingots, the production method comprising smelting, ingot casting, heating, rolling, stacking and slow cooling, and normalizing heat treatment processes; the normalizing heat treatment process: heating must be sufficient, normalizing temperature is 900-910℃, holding time is 1.8-2.1 min / mm; after normalizing, water cooling is used for accelerated cooling, cooling rate is 0.8-2℃ / s.

[0015] The smelting process described in this invention is as follows: the C content of the tapped steel is ≥0.06%, the increase in P element content from tapping to the end of LF refining is ≤0.005%, the vacuum degree is ≤66Pa and the holding time is ≥20min, and the soft blowing time after vacuum is ≥12min.

[0016] The casting process described in this invention involves using a good one-piece steel ingot mold, with a superheat of 43-47°C during casting, demolding after ≥14 hours of casting, and the ingot temperature after demolding must be ≥300°C.

[0017] The heating process described in this invention involves heating in a homogenizing furnace for 15 to 20 hours at a homogenizing temperature of 1240 to 1260°C.

[0018] The rolling process described in this invention adopts a two-stage controlled rolling process, with the steel thickness being H + (70~75) mm, where H is the thickness of the finished steel plate, and the final rolling temperature of the second stage being ≤850℃.

[0019] The slow cooling process of stacking described in this invention: the initial stacking temperature is 330-450℃, and the stacking time is ≥24h.

[0020] The chemical composition design of the steel plate of this invention is as follows: A medium-carbon (C) and high-mn (Mn) composition is adopted to enhance the strength of the steel plate through solid solution strengthening. Low Mn content will affect the solid solution strengthening effect, while excessive C content will affect low-temperature impact performance. Si acts as a deoxidizer and reducing agent in steelmaking, and its oxides are also a component of slag. Si also plays a role in solid solution strengthening, but when it exceeds 0.45%, it will cause a decrease in the toughness of the steel and a deterioration in its weldability. Al is used as a good deoxidizer and reducing agent in steelmaking. Simultaneously, its nitrides (AlN) can act as heterogeneous nucleation nuclei during the solidification of molten steel, promoting grain nucleation, thereby refining the grains, increasing the grain boundary ratio, and enhancing the grain boundary strengthening effect. During rolling and cooling, Al nitrides generate pinning forces on grain boundaries and dislocations, hindering grain boundary migration and increasing dislocation movement resistance, thus inhibiting grain growth and further enhancing the grain refinement strengthening effect. P causes low-temperature brittleness in the steel plate and has a significant impact on low-temperature impact toughness; therefore, the P content must be strictly controlled. Sulfur is a harmful element in this steel, reducing its ductility and toughness and causing cracks during rolling. The sulfur content in the steel should be minimized.

[0021] The beneficial effects of adopting the above technical solution are as follows: 1. The chemical composition of the steel plate of the present invention is designed with medium carbon, high manganese, and high aluminum, controlling the harmful elements P and S in the steel to a low level. The ultra-high aluminum content refines the grains, increases the precipitation of the second phase, replaces Nb and Ni, reduces costs and stabilizes performance, improves the internal quality of the steel plate, and the water cooling of the steel plate after normalizing and heat preservation ensures good mechanical properties of the steel plate, effectively enhancing market competitiveness. 2. The method of the present invention adopts strict control of steel tapping conditions and fine smelting process. The ultra-high aluminum content refines the grains and improves the internal quality of the steel plate, which can make the average reduction of area of ​​the thick tensile test sample of the steel plate ≥25%. The method of the present invention adopts the process of accelerated cooling after normalizing and heat preservation to obtain a metallographic structure of ferrite + pearlite + a small amount of bainite. The present invention obtains a steel plate with an average impact energy of ≥80J at -50℃ through a combination of smelting and rolling. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to specific embodiments.

[0023] A method for producing high-Al content, high-strength, low-temperature A633D steel plates from ingots includes smelting, ingot casting, heating, rolling, slow cooling in stacks, and normalizing heat treatment processes; the processes for each step are described below: 1) Smelting Process: The process employs electric furnace smelting, LF refining, and VD vacuum treatment. In the electric furnace smelting process, high-quality furnace charge is used, with a carbon content ≥0.06% at tapping. The phosphorus content increase from tapping to the end of LF refining is ≤0.005%, and no slag is allowed at tapping. During the tapping process from the electric furnace or converter, 0.5-1.5t of silicon-manganese alloy is added and controlled. In the LF refining process, the steel from the electric furnace or converter is transferred to the LF refining furnace for further refining, maintaining white slag for ≥30 minutes. Large-scale argon agitation is prohibited in the later stages of refining to avoid exposing the molten steel. In the VD vacuum treatment process, the vacuum level is ≤66Pa, and the holding time is ≥20 minutes; after vacuum breaking, soft blowing is performed for 12 minutes or more. The VD vacuum treatment process ensures that the elemental composition of the molten steel is as follows: C: 0.14–0.17%, Si: 0.20–0.45%, Mn: 1.45–1.60%, P≤0.012%, S≤0.003%, Alt: 0.25–0.50%, with the balance being Fe and trace amounts of unavoidable impurities. Extending the white slag holding time, vacuum holding time, and soft blowing time during the above process can further improve the cleanliness of the molten steel.

[0024] 2) Molding process: Use a good one-piece steel ingot mold, with a superheat of 43-47℃ during casting, demold after ≥14 hours of casting, and the temperature of the steel ingot after demolding must be ≥300℃.

[0025] 3) Heating process: The steel ingot is heated and held at different temperature ranges in a soaking furnace for 15 to 20 hours at a soaking temperature of 1240 to 1260°C to ensure uniform and thorough heating.

[0026] 4) Rolling process: A two-stage rolling process of recrystallization zone + non-recrystallization zone is adopted; the first stage is the rough rolling stage; the thickness of the steel plate is H+(70~75)mm, where H is the thickness of the finished steel plate; the final rolling temperature of the second stage is ≤850℃.

[0027] 5) Stacking and slow cooling process: After the steel plate is rolled, it is promptly taken off the production line and stacked for slow cooling. The initial stacking temperature is 330-450℃, and the stacking time is ≥24h, which is conducive to the diffusion and elimination of N and H elements and the release of stress in the steel plate.

[0028] 6) Normalizing heat treatment process: Heating must be sufficient, normalizing temperature 900~910℃, holding time 1.8-2.1min / mm; after normalizing, water cooling is accelerated, cooling rate 0.8~2℃ / s.

[0029] The chemical composition and mass percentage of the obtained A633D steel plate are the same as those of the molten steel produced by the VD vacuum treatment process. The steel plate thickness is 60-110mm, and the flaw detection meets the acceptance level Level I of GB / T2970-2016. The metallographic structure is ferrite + pearlite + a small amount of bainite. The properties are: yield strength ≥339MPa, tensile strength 490-550MPa, elongation ≥24%, average longitudinal impact energy at -50℃ greater than 80J, and reduction of area ≥25% for thick tensile sections. Example 1

[0030] A method for producing high-Al content, high-strength, low-temperature A633D steel plates from ingots includes smelting, ingot casting, heating, rolling, slow cooling in stacks, and normalizing heat treatment processes; the processes for each step are described below: 1) Smelting Process: The process employs electric furnace smelting, LF refining, and VD vacuum treatment. In the electric furnace smelting process, high-quality furnace charge is used, with a tapped steel C content of 0.109% and a tapped steel P content of 0.010%. The P content increase from tapping to the end of LF refining is 0.002%, and no slag is added during tapping. 1 t of silicon-manganese alloy is added during the tapping process in the electric furnace or converter. In the LF refining process, the steel tapped from the electric furnace or converter is transferred to the LF refining furnace for refining, with white slag maintained for 30 minutes. Large-scale argon agitation is avoided in the later stages of refining to prevent the molten steel from being exposed. In the VD vacuum treatment process, the vacuum level is 66 Pa, maintained for 20 minutes, followed by soft blowing for 12 minutes after vacuum breaking. The VD vacuum treatment process ensures that the elemental composition of the molten steel is: C: 0.17%, Si: 0.34%, Mn: 1.45%, P: 0.012%, S: 0.0013%, Alt: 0.25%, with the balance being Fe and trace amounts of unavoidable impurities.

[0031] 2) Molding process: A good one-piece steel ingot mold is used. The superheat during casting is 43℃. The ingot is demolded after 15 hours of casting. The temperature of the steel ingot after demolding is 430℃.

[0032] 3) Heating process: The steel ingot is heated and held at different temperature ranges in a soaking furnace for 18 hours. The maximum heating temperature of the steel ingot is 1260℃, and the soaking temperature is 1240℃ to ensure uniform and thorough heating.

[0033] 4) Rolling process: A two-stage rolling process of recrystallization zone + non-recrystallization zone is adopted; the first stage is the rough rolling stage; the steel thickness is 172mm; the rolling temperature at the beginning of the second stage is 900℃; and the final rolling temperature of the second stage is 848℃.

[0034] 5) Stacking and slow cooling process: After the steel plates are rolled, they are promptly taken off the production line and stacked for slow cooling. The initial stacking temperature is 401℃ and the stacking time is 36 hours.

[0035] 6) Normalizing heat treatment process: Heating must be sufficient, normalizing temperature 900℃, holding time 1.9min / mm; after normalizing, water cooling is used to accelerate cooling, cooling rate 2℃ / s.

[0036] The chemical composition and mass percentage of the obtained A633D steel plate are the same as those of the molten steel produced by the VD vacuum treatment process. The steel plate thickness is 102mm, and the flaw detection meets the acceptance level Level I of GB / T2970-2016. The metallographic structure is ferrite + pearlite + 20% bainite. The properties are: yield strength 380MPa, tensile strength 520MPa, elongation 27.5%, average longitudinal impact energy at -50℃ 83J, and reduction of area of ​​thick tensile sections 28%, 34%, and 25%. Example 2

[0037] A method for producing high-Al content, high-strength, low-temperature A633D steel plates from ingots includes smelting, ingot casting, heating, rolling, slow cooling in stacks, and normalizing heat treatment processes; the processes for each step are described below: 1) Smelting Process: The process employs electric furnace smelting, LF refining, and VD vacuum treatment. In the electric furnace smelting process, high-quality furnace charge is used, with a tapped steel C content of 0.067% and a tapped steel P content of 0.007%. The P content increases to 0.002% from tapping to the end of LF refining, and no slag is added during tapping. 0.5t of silicon-manganese alloy is added during the tapping process in the electric furnace or converter. In the LF refining process, the steel tapped from the electric furnace or converter is transferred to the LF refining furnace for further refining, maintaining white slag for 38 minutes. Large-scale argon agitation is avoided in the later stages of refining to prevent the molten steel from being exposed. In the VD vacuum treatment process, the vacuum level is 60 Pa, maintained for 24 minutes, followed by soft blowing for 13 minutes after vacuum breaking. The VD vacuum treatment process ensures that the elemental composition of the molten steel is: C: 0.16%, Si: 0.28%, Mn: 1.49%, P: 0.010%, S: 0.0020%, Alt: 0.29%, with the balance being Fe and trace amounts of unavoidable impurities.

[0038] 2) Molding process: A good one-piece steel ingot mold is used. The superheat during casting is 44℃. The ingot is demolded after 16 hours of casting. The temperature of the steel ingot after demolding is 440℃.

[0039] 3) Heating process: The steel ingot is heated and held at different temperature ranges in a soaking furnace for 15 hours. The maximum heating temperature of the steel ingot is 1260℃, and the soaking temperature is 1250℃ to ensure uniform and thorough heating.

[0040] 4) Rolling process: A two-stage rolling process of recrystallization zone + non-recrystallization zone is adopted; the first stage is the rough rolling stage; the steel thickness is 150mm; the rolling temperature at the beginning of the second stage is 887℃; and the final rolling temperature of the second stage is 835℃.

[0041] 5) Stacking and slow cooling process: After the steel plates are rolled, they are promptly taken off the production line and stacked for slow cooling. The initial stacking temperature is 424℃ and the stacking time is 24 hours.

[0042] 6) Normalizing heat treatment process: Heating must be sufficient, normalizing temperature 910℃, holding time 1.8min / mm; after normalizing, water cooling is used to accelerate cooling, cooling rate 1℃ / s.

[0043] The chemical composition and mass percentage of the obtained A633D steel plate are the same as those of the molten steel produced by the VD vacuum treatment process. The steel plate thickness is 76mm, and the flaw detection meets the acceptance level I of GB / T2970-2016. The metallographic structure is ferrite + pearlite + 10% bainite. The properties are: yield strength 380MPa, tensile strength 520MPa, elongation 27.5%, average longitudinal impact energy at -50℃ 111J, and reduction of area of ​​thick tensile sections 27%, 31%, and 30%. Example 3

[0044] A method for producing high-Al content, high-strength, low-temperature A633D steel plates from ingots includes smelting, ingot casting, heating, rolling, slow cooling in stacks, and normalizing heat treatment processes; the processes for each step are described below: 1) Smelting Process: The process employs electric furnace smelting, LF refining, and VD vacuum treatment. In the electric furnace smelting process, high-quality furnace charge is used. The tapped steel contains 0.076% C and 0.009% P. The P content increases to 0.003% by the end of LF refining, and no slag is added during tapping. 0.7t of silicon-manganese alloy is added during the tapping process in either the electric furnace or converter. In the LF refining process, the steel is transferred from the electric furnace or converter to the LF refining furnace for further refining, maintaining white slag for 30 minutes. Large-scale argon agitation is avoided in the later stages of refining to prevent the molten steel from being exposed. In the VD vacuum treatment process, the vacuum level is 62 Pa, and the holding time is 22 minutes. After vacuum breaking, soft blowing is performed for 13 minutes. The VD vacuum treatment process ensures the elemental composition of the tapped steel is: C: 0.14%, Si: 0.45%, Mn: 1.60%, P: 0.011%, S: 0.003%, Alt: 0.37%, with the balance being Fe and trace amounts of unavoidable impurities.

[0045] 2) Molding process: A good one-piece steel ingot mold is used. The superheat during casting is 45°C. The ingot is demolded after 17 hours of casting. The temperature of the steel ingot after demolding is 300°C.

[0046] 3) Heating process: The steel ingot is heated and held at different temperature ranges in a soaking furnace for 17 hours. The maximum heating temperature of the steel ingot is 1260℃, and the soaking temperature is 1260℃ to ensure uniform and thorough heating.

[0047] 4) Rolling process: A two-stage rolling process of recrystallization zone + non-recrystallization zone is adopted; the first stage is the rough rolling stage; the steel thickness is 147mm; the rolling temperature at the beginning of the second stage is 868℃; the final rolling temperature of the second stage is 821℃.

[0048] 5) Stacking and slow cooling process: After the steel plates are rolled, they are promptly taken off the production line and stacked for slow cooling. The initial stacking temperature is 330℃ and the stacking time is 25 hours.

[0049] 6) Normalizing heat treatment process: Heating must be sufficient, normalizing temperature 900℃, holding time 1.9min / mm; after normalizing, water cooling is used to accelerate cooling, cooling rate 0.9℃ / s.

[0050] The chemical composition and mass percentage of the obtained A633D steel plate are the same as those of the molten steel produced by the VD vacuum treatment process. The steel plate thickness is 72mm, and the flaw detection meets the acceptance level I of GB / T2970-2016. The metallographic structure is ferrite + pearlite + 14% bainite. The properties are: yield strength 398MPa, tensile strength 539MPa, elongation 25.5%, average longitudinal impact energy at -50℃ 100J, and reduction of area of ​​thick tensile sections 27%, 34%, and 30%. Example 4

[0051] A method for producing high-Al content, high-strength, low-temperature A633D steel plates from ingots includes smelting, ingot casting, heating, rolling, slow cooling in stacks, and normalizing heat treatment processes; the processes for each step are described below: 1) Smelting Process: The process employs electric furnace smelting, LF refining, and VD vacuum treatment. In the electric furnace smelting process, high-quality furnace charge is used. The steel output contains 0.086% C and 0.008% P. The P content increases to 0.0031% from tapping to the end of LF refining, and no slag is added during tapping. 1.5t of silicon-manganese alloy is added during the tapping process in the electric furnace or converter. In the LF refining process, the steel from the electric furnace or converter is transferred to the LF refining furnace for further refining, maintaining white slag for 32 minutes. Large-scale argon agitation is avoided in the later stages of refining to prevent the molten steel from being exposed. In the VD vacuum treatment process, the vacuum level is 58 Pa, maintained for 23 minutes, followed by soft blowing for 12 minutes after vacuum breaking. The VD vacuum treatment process ensures that the elemental composition of the molten steel is: C: 0.15%, Si: 0.20%, Mn: 1.48%, P: 0.012%, S: 0.0015%, Alt: 0.50%, with the balance being Fe and trace amounts of unavoidable impurities.

[0052] 2) Molding process: A good one-piece steel ingot mold is used. The superheat during pouring is 47°C. The ingot is demolded after 14 hours of pouring. The temperature of the steel ingot after demolding is 340°C.

[0053] 3) Heating process: The steel ingot is heated and held at different temperature ranges in a soaking furnace for 20 hours. The maximum heating temperature of the steel ingot is 1260℃, and the soaking temperature is 1240℃ to ensure uniform and thorough heating.

[0054] 4) Rolling process: A two-stage rolling process of recrystallization zone + non-recrystallization zone is adopted; the first stage is the rough rolling stage; the steel thickness is 180mm; the rolling temperature at the beginning of the second stage is 891℃; the final rolling temperature of the second stage is 850℃.

[0055] 5) Stacking and slow cooling process: After the steel plates are rolled, they are promptly taken off the production line and stacked for slow cooling. The initial stacking temperature is 450℃ and the stacking time is 25 hours.

[0056] 6) Normalizing heat treatment process: Heating must be sufficient, normalizing temperature 905℃, holding time 2min / mm; after normalizing, water cooling is used to accelerate cooling, cooling rate 2.1℃ / s.

[0057] The chemical composition and mass percentage of the obtained A633D steel plate are the same as those of the molten steel produced by the VD vacuum treatment process. The steel plate thickness is 110mm, and the flaw detection meets the acceptance level I of GB / T2970-2016. The metallographic structure is ferrite + pearlite + 23% bainite. The properties are: yield strength 373MPa, tensile strength 524MPa, elongation 27.5%, average longitudinal impact energy at -50℃ 86J, and reduction of area of ​​thick tensile sections 24%, 28%, and 25%.

[0058] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-Al content, high-strength, low-temperature A633D steel plate, characterized in that, The chemical composition and mass percentage of the A633D steel plate are as follows: C: 0.14~0.17%, Si: 0.20~0.45%, Mn: 1.45~1.60%, P≤0.012%, S≤0.003%, Alt: 0.25~0.50%, with the balance being Fe and trace amounts of unavoidable impurities.

2. The high-strength, low-temperature A633D steel plate with ultra-high Al content as described in claim 1, characterized in that, The metallographic structure of the steel plate is ferrite + pearlite + a small amount of bainite, of which bainite accounts for 10-23%.

3. A high-strength, low-temperature A633D steel plate with ultra-high Al content as described in claim 1 or 2, characterized in that: The steel plate has a thickness of 60-110mm, and the flaw detection meets the acceptance level I of GB / T2970-2016.

4. The high-strength, low-temperature A633D steel plate with ultra-high Al content as described in claim 1 or 2, characterized in that, The steel plate has the following properties: yield strength ≥339MPa, tensile strength 490~550MPa, elongation ≥24%, average longitudinal impact energy at -50℃ ≥80J, and reduction of area ≥25% for thick tensile sections.

5. A method for producing ultra-high Al content high-strength low-temperature A633D steel plates based on any one of claims 1-4, characterized in that: The production method includes smelting, ingot casting, heating, rolling, stacking and slow cooling, and normalizing heat treatment processes; The normalizing heat treatment process requires: sufficient heating, a normalizing temperature of 900-910℃, and a holding time of 1.8-2.1 min / mm; after normalizing, water cooling is used to accelerate cooling at a rate of 0.8-2℃ / s.

6. The method for producing ultra-high Al content high-strength low-temperature A633D steel plate from ingots according to claim 5, characterized in that, The smelting process is as follows: the C content of the tapped steel is ≥0.06%, the increase in P content from tapping to the end of LF refining is ≤0.005%, the vacuum degree is ≤66Pa and the holding time is ≥20min, and the soft blowing time after vacuum is ≥12min.

7. The method for producing ultra-high Al content high-strength low-temperature A633D steel plate from ingots according to claim 5, characterized in that, The casting process involves using a high-quality integrated steel ingot mold, with a superheat of 43-47°C during casting, followed by demolding after ≥14 hours of casting, and the ingot temperature must be ≥300°C after demolding.

8. The method for producing ultra-high Al content high-strength low-temperature A633D steel plate from ingots according to claim 5, characterized in that, The heating process involves heating in a homogenizing furnace for 15–20 hours at a homogenizing temperature of 1240–1260°C.

9. A method for producing ultra-high Al content high-strength low-temperature A633D steel plate from ingots according to any one of claims 5-8, characterized in that, The rolling process adopts a two-stage controlled rolling process, with the steel thickness being H + (70~75) mm, where H is the thickness of the finished steel plate, and the final rolling temperature of the second stage being ≤850℃.

10. A method for producing high-strength, low-temperature A633D steel plate with ultra-high Al content according to any one of claims 5-8, characterized in that, The stacking slow cooling process: the initial stacking temperature is 330-450℃, and the stacking time is ≥24h.