High-strength anti-seismic steel bar

Abstract

This invention discloses a high-strength earthquake-resistant steel bar, relating to the field of building steel technology. It is composed of the following components by weight percentage: C: 0.16-0.19%, Si: 0.35-0.50%, Mn: 1.25-1.40%, V: 0.025-0.035%, N: 0.0060-0.0085%, Cu: 0.18-0.25%, Cr: 0.25-0.35%, Mo: 0.04-0.08%, composite rare earth: 0.010-0.018%, B: 0.0010-0.0020%, Ti: 0.008-0.015%, with the remainder being Fe. Impurity content is controlled as follows: P≤0.020%, S≤0.008%, O≤0.0020%. The sum of the weight percentages of all components is 100%. The steel bars prepared by this invention have good mechanical properties and corrosion resistance, and can meet the stringent seismic requirements of high-intensity earthquake zones.

Description

Technical Field

[0001] The present invention relates to the technical field of construction steel, in particular to a high-strength anti-seismic steel bar. Background Art

[0002] Concrete is used in a huge volume in the field of construction engineering. As the core matching steel material for concrete, the demand for steel bars continues to rise. The mainstream products cover two categories: ordinary hot-rolled ribbed steel bars, and prestressed steel wires and steel strands. Among them, the grades of hot-rolled ribbed steel bars mainly include HRB335, HRB400 and HRB500. The letters H, R and B correspond to Hot rolled, Ribbled and Bars in sequence, and the following number represents the minimum yield strength of the steel bar (unit: MPa). The adoption of high-strength steel bars can not only reduce the unit consumption of steel and reduce the self-weight of buildings, but also improve the structural safety and service durability of buildings, and achieve cost reduction and efficiency increase in the whole life cycle of the project.

[0003] At this stage, due to the low yield strength of HRB335 steel bars, when used in high-rise buildings, elevated overpasses, roads, bridge culverts and other projects, they have problems such as large self-weight, low utilization rate of structural bearing, and serious steel waste, so they are gradually being eliminated. HRB400 and HRB500 steel bars have become mainstream application varieties. To meet the seismic requirements of buildings, the application scope of HRB400E and HRB500E high-strength anti-seismic steel bars has been further expanded, and they have become the core materials for seismic fortification projects.

[0004] However, ordinary HRB400E steel bars have fast corrosion rate and short service life in corrosive environments such as offshore areas, acid rain areas and chemical industries. Conventional protection mostly relies on epoxy coating or galvanizing treatment. However, the coating is easily damaged and peeled off during construction and handling, and the corrosion rate of the steel bar will increase sharply after the protection fails. Existing corrosion-resistant anti-seismic steel bars mostly adopt Cu-Cr-Ni-Mo alloying system, which relies on high-cost Ni element to improve corrosion resistance, thus increasing the production cost of steel bars; and although excessive addition of Cr and Ni improves corrosion resistance, it easily causes abnormal grain coarsening and deterioration of matrix plasticity, resulting in that the elongation of the steel bar fails to meet the standard, and it is difficult to meet the high ductility requirements of anti-seismic steel bars.

[0005] From a manufacturing process perspective, traditional high-strength earthquake-resistant steel bars employ a crude controlled rolling and cooling process with fixed water pressure and constant temperature cooling. This process cannot dynamically adapt to billet temperature fluctuations, easily leading to problems such as uneven internal structure, large deviations in mechanical properties at the beginning and end, low strength-to-yield ratio, and decreased elongation. This fails to meet the stringent earthquake-resistant requirements of high ductility and high energy absorption in high-intensity earthquake zones. Furthermore, the traditional rapid cooling process lacks a matching tempering recovery stage, easily inducing the formation of excessive brittle martensite and bainite structures. The high residual stress within the steel bars not only exacerbates stress corrosion cracking but also increases the risk of sudden brittle fracture during service. Rare earth elements (such as La and Ce) can spheroidize MnS strip-shaped inclusions, purify grain boundaries, effectively inhibit inclusion-induced localized corrosion, and improve the strength and toughness of the steel bars. However, rare earth elements are extremely reactive in chemistry and readily react with O, S and slag in molten steel at high temperatures, generating rare earth oxides that are lost as slag. This prevents them from fully utilizing their role in inclusion degradation and grain boundary purification, and thus fails to effectively solve the problem of localized corrosion induced by inclusions such as MnS.

[0006] Therefore, it is difficult to achieve a balance between corrosion resistance, high ductility, high strength and toughness, and low cost in current high-strength earthquake-resistant steel bars. How to break through the existing technical bottlenecks and develop high-performance steel bars with both excellent corrosion resistance and earthquake ductility is of great research value and application prospects for promoting the improvement of quality and efficiency in construction projects and extending the service life of structures. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a high-strength earthquake-resistant steel bar.

[0008] The objective of this invention can be achieved through the following technical solutions: A high-strength earthquake-resistant steel bar, by weight percentage, is composed of the following components: C: 0.16-0.19%, Si: 0.35-0.50%, Mn: 1.25-1.40%, V: 0.025-0.035%, N: 0.0060-0.0085%, Cu: 0.18-0.25%, Cr: 0.25-0.35%, Mo: 0.04-0.08%, composite rare earth: 0.010-0.018%, B: 0.0010-0.0020%, Ti: 0.008-0.015%, with the remainder being Fe. The impurity content is controlled as follows: P≤0.020%, S≤0.008%, O≤0.0020%, and the sum of the weight percentages of all components is 100%.

[0009] Furthermore, the composite rare earth is obtained by mixing La, Ce, and Y in a mass ratio of 2-2.5:3-3.5:1-1.5.

[0010] Furthermore, the production method of high-strength earthquake-resistant steel bars includes the following steps: Step (1): Heat pig iron to obtain molten iron, then add desulfurizing agent to molten iron, stir, let stand, remove the sulfur slag on top to obtain desulfurized molten iron; add dephosphorizing agent to desulfurized molten iron, control the temperature, blow argon gas from the bottom, and then remove phosphorus slag to obtain pretreated molten iron. Step (2): The pretreated molten iron is transferred into the converter and smelted using a top and bottom blowing process. Oxygen is blown from the top and argon is blown from the bottom. During the tapping process, ferromanganese and ferrosilicon are added, and slag is blocked during tapping to obtain primary molten steel. Step (3): The primary molten steel is fed into the LF refining furnace, and argon gas is blown from the bottom throughout the process. The refining furnace is heated up, and ferrochrome, ferrocopper, and ferromolybdenum are added to it in sequence and stirred and mixed. The temperature is lowered, and ferrovanadium and ferrotitanium are added and stirred to obtain alloyed molten steel. Step (4): Cool the alloyed steel liquid, use a sealed wire feeder, argon gas protection throughout the process, feed composite rare earth and boron cored wire at the same time, after the wire feeding is completed, let it stand, blow nitrogen gas from the bottom, and then transfer it to the vacuum chamber for degassing. After breaking the vacuum, keep it at the temperature to obtain refined molten steel. Step (5): The refined molten steel is continuously cast, the casting speed is controlled, and the electromagnetic stirring of the crystallizer is turned on to obtain the continuously cast billet; after the continuously cast billet is naturally cooled on the sealed slow cooling pit, it is transferred to the room temperature area and cooled to room temperature, and then cut into steel billets to obtain the continuously cast steel billet. Step (6): Place the continuously cast steel billet in a walking beam furnace and use a three-stage gradient heating process, then perform an integrated process of adaptive controlled rolling-variable pressure water cooling to obtain rolled steel bars; perform temperature-controlled stacking cooling on the rolled steel bars to obtain high-strength earthquake-resistant steel bars.

[0011] Furthermore, the production method of high-strength earthquake-resistant steel bars includes the following specific steps: Step (1): Heat pig iron from room temperature to 1400-1450℃ and hold for 30-50 minutes to obtain molten iron. Then add desulfurizing agent to the molten iron and stir at 130-150 rpm for 10-12 minutes. Let it stand for 5-7 minutes and remove the top sulfur slag to obtain desulfurized molten iron with S≤0.008%. Add dephosphorizing agent to the desulfurized molten iron, control the temperature at 1300-1380℃, and remove the phosphorus slag by bottom blowing argon gas to obtain pretreated molten iron with P≤0.020%. Furthermore, the desulfurizing agent is obtained by mixing calcium oxide and sodium carbonate in a mass ratio of 6-7:2-3; the dephosphorizing agent is obtained by mixing iron oxide scale, lime, and fluorite in a mass ratio of 2.5-3.5:5-7:0.8-1.0.

[0012] Furthermore, the ratio of molten iron to desulfurizing agent is 1t: 18-20kg; the ratio of desulfurized molten iron to dephosphorizing agent is 1t: 8-10kg.

[0013] Step (2): Transfer the pretreated molten iron into the converter at an inlet temperature of 1400-1500℃. Use a top-and-bottom blowing process for refining, with oxygen blowing from the top and argon blowing from the bottom. Tap the steel when the temperature reaches 1640-1660℃. Add ferromanganese and ferrosilicon during tapping, and simultaneously remove slag during tapping to obtain primary molten steel. The primary molten steel has the following composition: O ≤ 0.0020%, Mn: 1.25-1.40%, Si: 0.35-0.50%. Furthermore, the flow rate of top-blown oxygen is controlled at 3.5-4.5 Nm³ / (min·t), and the flow rate of bottom-blown argon is controlled at 0.3-0.6 Nm³ / (min·t).

[0014] Step (3): The primary molten steel is fed into the LF refining furnace, and argon gas is blown from the bottom throughout the process. The temperature of the refining furnace is raised to 1610-1630℃. Ferrochrome, ferrocopper, and ferromolybdenum are added in sequence. Each addition of a component is stirred for 4-6 minutes. After all the ferrochrome, ferrocopper, and ferromolybdenum are added, the mixture is stirred for 3-5 minutes. The concentrations of Cu, Cr, and Mo are controlled at 0.18-0.25%, 0.25-0.35%, and 0.04-0.08%. The temperature is then lowered to 1580-1600℃. Ferrovanadium and ferrotitanium are added and stirred for 2-3 minutes. The concentrations of V, Ti, and Ti are controlled at 0.025-0.035% and 0.008-0.015%, respectively, to obtain alloyed steel liquid. Step (4): Cool the alloyed steel liquid to 1570-1590℃, use a sealed wire feeder, and feed composite rare earth and boron cored wires at the same time under argon protection. After the wire feeding is completed, let it stand for 8-10 minutes, and control N: 0.0060-0.0085% by bottom blowing nitrogen. Then transfer it to the vacuum chamber, evacuate to a vacuum degree ≤67Pa, maintain the vacuum for 13-15 minutes, and bottom blow argon throughout. After breaking the vacuum, keep it at 1590-1620℃ for 8-12 minutes to obtain refined molten steel. Furthermore, the wire feeding speed for simultaneously feeding composite rare earth and boron cored wire is as follows: 2.0-2.5 m / s into the furnace in the early stage, and 3.0-3.5 m / s into the alloyed steel liquid in the later stage. The wire feeding depth is 60% of the depth of the alloyed steel liquid, the wire feeding angle is ≤15° inclined, and the outer diameter of the boron cored wire is 13-16 mm.

[0015] Furthermore, the initial length is 1 / 3 to 1 / 2 of the length before feeding, and the later length is 1 / 2 to 2 / 3 of the length after feeding.

[0016] Step (5): The refined molten steel is continuously cast at a temperature of 15-25℃ with a superheat of molten steel. The casting speed is controlled at 1.8-2.4m / min. The electromagnetic stirring of the crystallizer is turned on and stirred for 3-5 minutes to obtain a continuously cast billet. The continuously cast billet is naturally cooled to ≤400℃ in a closed slow cooling pit, and then transferred to the room temperature area to continue cooling to room temperature. It is then cut into 6-12m steel billets to obtain continuously cast steel billets. Furthermore, the crystallizer used for electromagnetic stirring has a length of 0.9-1.2m and a stirring frequency of 3-5Hz.

[0017] Step (6): Place the continuously cast steel billet in a walking beam furnace and use a three-stage gradient heating process, then perform an integrated process of adaptive controlled rolling-variable pressure water cooling to obtain rolled steel bars; perform temperature-controlled stacking cooling on the rolled steel bars to obtain high-strength earthquake-resistant steel bars.

[0018] Furthermore, the three-stage gradient heating is as follows: preheating stage: heating to 800-900℃ within 35-40 minutes and holding for 10-15 minutes; heating stage: heating to 1140-1170℃ within 30-35 minutes and holding for 20-25 minutes; and soaking stage: holding at 1150-1170℃ for 50-60 minutes.

[0019] Furthermore, the adaptive controlled rolling-variable pressure water cooling integrated process is specifically as follows: (1) Rough rolling and intermediate rolling: The initial rolling temperature is 1030-1060℃, and the total reduction rate is 60-65%; the temperature of the rough rolling stage is controlled at 990-1040℃, and the temperature of the intermediate rolling stage is controlled at 920-990℃. (2) Pre-finishing rolling controlled cooling: a single-stage variable pressure water cooling system is adopted, with a water pressure of 0.7-0.9MPa, a cooling section length of 4m, a uniform temperature section length of 25m, and the temperature of the rolled piece entering the pre-finishing rolling mill is controlled at 870-900℃; (3) Finishing rolling: The temperature of the rolled piece entering the finishing rolling mill is controlled at 840-860℃, and the total reduction rate is 40-48%; (4) Final rolling multi-stage controlled cooling: Two-stage variable pressure water cooling is adopted, with a water pressure of 1.9-2.3MPa. First, it is cooled to 710-740℃, then enters the tempering section and is held at 690-710℃ for 5-15 minutes, and then cooled to 630-660℃.

[0020] Furthermore, the temperature-controlled stack cooling process involves placing the rolled steel bars on a cooling bed, first air cooling them to 530-550℃, and then transferring them to a sealed slow cooling pit for slow cooling to room temperature at a rate of ≤40℃ / h. The entire stack cooling process takes 24-36 hours.

[0021] This invention discloses a high-strength earthquake-resistant steel bar, which is composed of the following components by weight percentage: C: 0.16-0.19%, Si: 0.35-0.50%, Mn: 1.25-1.40%, V: 0.025-0.035%, N: 0.0060-0.0085%, Cu: 0.18-0.25%, Cr: 0.25-0.35%, Mo: 0.04-0.08%, composite rare earth: 0.010-0.018%, B: 0.0010-0.0020%, Ti: 0.008-0.015%, with the remainder being Fe. The impurity content is controlled as follows: P≤0.020%, S≤0.008%, O≤0.0020%, and the sum of the weight percentages of all components is 100%. The production method is as follows: pig iron is melted into molten iron, which is then treated with desulfurizing and dephosphorizing agents to obtain pretreated molten iron; the pretreated molten iron is transferred to a converter and smelted using a top-and-bottom combined blowing process, with ferromanganese and ferrosilicon added during tapping to obtain primary molten steel; the primary molten steel is sent to an LF refining furnace, where ferrochrome, ferrocopper, and ferromolybdenum are added sequentially, followed by cooling and the addition of ferrovanadium and ferrotitanium to obtain alloyed molten steel; composite rare earth and boron cored wire are simultaneously fed into the alloyed molten steel, and nitrogen is then blown at the bottom to control the nitrogen content, followed by vacuum degassing to obtain refined molten steel; the refined molten steel is continuously cast, then slowly cooled in a sealed environment and cut into sections to obtain continuously cast steel billets; the continuously cast steel billets are heated using a three-stage gradient heating process, followed by an adaptive controlled rolling-variable pressure water cooling integrated process to obtain rolled steel bars; the rolled steel bars are then subjected to temperature-controlled stacking cooling to obtain high-strength earthquake-resistant steel bars.

[0022] It has the following beneficial effects: 1. This invention abandons the crude approach of simply adding expensive alloying elements (such as high proportions of Ni and Mo) to enhance the corrosion resistance of high-strength earthquake-resistant steel bars. Instead, it uses appropriate amounts of Cu (0.18-0.25%) and Cr (0.25-0.35%) as the core to form a dense Cu-Cr composite oxide film, serving as the first line of defense against atmospheric and chloride ion corrosion. The introduction of trace amounts of Mo (0.04-0.08%) effectively replaces the role of high-cost Ni, significantly improving the pitting corrosion resistance of the steel bars in acidic or chloride-containing environments, while avoiding the increased cost and decreased workability caused by high Mo, thus achieving an optimized balance between performance and cost. This invention employs a rare earth-boron-vanadium-titanium microalloying combination. A composite rare earth element (0.010-0.018%) composed of La, Ce, and Y, synergistically works with trace amounts of B (0.0010-0.0020%). The rare earth elements deeply purify the molten steel, transforming harmful Al2O3 and MnS inclusions into fine, dispersed, spherical rare earth oxides and sulfides, eliminating stress concentration sources. Simultaneously, B atoms agglomerate at grain boundaries, working synergistically with the rare earth elements to "fill" grain boundary defects, significantly improving grain boundary properties. Strength is enhanced by inhibiting crack propagation along grain boundaries, thereby fundamentally improving toughness. The combined addition of V (0.025-0.035%) and Ti (0.008-0.015%) precipitates fine V(C,N) and TiN / C particles during controlled rolling and cooling. These nanoscale precipitates not only strongly pin the austenite grain boundaries and refine the final ferrite grains (fine grain strengthening), but they are also effective precipitate strengthening phases themselves. Together with the grain boundary strengthening mechanism, they jointly construct the high-strength foundation of the steel reinforcement.

[0023] 2. In the production process of the high-strength earthquake-resistant steel bars of this invention, a mechanical stirring desulfurization + molten iron ladle blowing dephosphorization process is adopted to achieve deep purification of molten iron, laying a solid foundation for subsequent high-purity smelting. In the LF refining process, the order of "adding medium-strong carbide-forming elements such as Cu, Cr, and Mo first, and then adding strong carbonitride-forming elements such as V and Ti" is followed, and the argon stirring intensity is adjusted in stages to ensure efficient melting and uniform distribution of each element. The key rare earth and boron elements adopt a variable-speed wire feeding technology of "low-speed furnace input in the early stage and high-speed deep burial in the later stage", which effectively improves the yield and uniformity of these two easily oxidized and burned-off elements, and achieves precise control of the liquid crystal interface and inclusions in the steel. After wire feeding alloying, nitrogen is first precisely controlled by bottom blowing nitrogen, and then high-vacuum degassing is used to deeply remove H, O and fine inclusions, significantly improving the density and resistance to hydrogen-induced cracking of the steel.

[0024] 3. The billet heating method of this invention adopts a three-stage process of "preheating-heating-homogenization." Through slow heating and sufficient heat preservation, it ensures uniform core-surface temperature and homogenization of the original austenite composition, providing an ideal initial microstructure for subsequent controlled rolling. Rough rolling is performed at 990-1040℃, and intermediate rolling at 920-990℃, using a total reduction rate of 60-65%, to fully break down the as-cast microstructure and refine the austenite grains. Pre-finish rolling and finish rolling are then performed, with precise control over the phase transformation process of the deformed austenite through a first-stage variable-pressure water quenching (870-900℃ inlet) and a second-stage variable-pressure water quenching after final rolling. Furthermore, a two-stage variable pressure water cooling process is immediately performed after final rolling: the first stage involves rapid cooling under high pressure (1.9-2.3MPa) to 710-740℃ to suppress proeutectoid ferrite and promote bainitic phase transformation; the second stage involves entering the tempering section (690-710℃) and holding for 5-15 minutes. This "gradient recovery process" relaxes the internal stress of the microstructure, allows carbides to fully precipitate and spheroidize, and avoids excessive grain growth; finally, the microstructure is cooled to 630-660℃ to obtain a multiphase microstructure mainly composed of fine lath bainite and containing dispersed carbides, thereby improving strength, toughness, and yield strength ratio. After rolling, a gradient cooling process is adopted, consisting of air cooling to medium temperature followed by slow cooling in a sealed pit: the steel is transferred to a slow cooling pit below 530-550℃ and cooled at a rate of ≤40℃ / h for 24-36 hours. This process is equivalent to a long-term low-temperature aging treatment, which further homogenizes internal stress, promotes the full precipitation of microalloyed carbonitrides, stabilizes the microstructure, completely eliminates the risk of delayed fracture, and slightly improves strength; it also improves energy utilization efficiency. Therefore, the resulting steel bars can meet the stringent seismic requirements of high ductility and high energy absorption in high-intensity earthquake zones. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1 A high-strength earthquake-resistant steel bar is composed of the following components by weight percentage: C: 0.16%, Si: 0.35%, Mn: 1.25%, V: 0.025%, N: 0.0060%, Cu: 0.18%, Cr: 0.25%, Mo: 0.04%, composite rare earth: 0.010%, B: 0.0010%, Ti: 0.008%, with the remainder being Fe. The impurity content is controlled as follows: P: 0.018%, S: 0.007%, O: 0.0018%. The sum of the weight percentages of all components is 100%.

[0027] A high-strength earthquake-resistant steel bar, the production method of which includes the following specific steps: Step (1): Heat pig iron from room temperature to 1400℃ and hold for 30 minutes to obtain molten iron. Then add desulfurizing agent to the molten iron and stir at 130 rpm for 10 minutes. Let it stand for 5 minutes and remove the top sulfur slag to obtain desulfurized molten iron with S: 0.007%. Add dephosphorizing agent to the desulfurized molten iron and control the temperature at 1300℃. Stir at 130 rpm for 12 minutes by bottom blowing argon (argon flow rate of 0.4 Nm³ / (min·t)). Remove the phosphorus slag to obtain pretreated molten iron with P: 0.018%. The ratio of molten iron to desulfurizing agent is 1t: 18kg. The desulfurizing agent is a mixture of calcium oxide and sodium carbonate in a mass ratio of 6:2. The ratio of desulfurized molten iron to dephosphorizing agent is 1t: 8kg. The dephosphorizing agent is a mixture of iron oxide scale, lime, and fluorite in a mass ratio of 2.5: 5: 0.8.

[0028] Step (2): The pretreated molten iron is transferred into the converter at a temperature of 1400℃. The top and bottom blowing process is used for smelting, with oxygen blown from the top and argon blown from the bottom. When the temperature reaches 1640℃, the steel is tapped. During the tapping process, ferromanganese and ferrosilicon are added, and slag is blocked during tapping to obtain primary molten steel. The primary molten steel has the following composition: O: 0.0018%, Mn: 1.25%, Si: 0.35%. The flow rate of top-blown oxygen is controlled at 3.5 Nm³ / (min·t), and the flow rate of bottom-blown argon is controlled at 0.3 Nm³ / (min·t).

[0029] Step (3): The primary molten steel is fed into the LF refining furnace, and argon is blown into the bottom throughout the process (argon flow rate is 0.32 Nm³ / (min·t)). The temperature of the refining furnace is raised to 1610℃, and ferrochrome, ferrocopper, and ferromolybdenum are added in sequence. Each addition of a component is stirred for 4 min, and after all the ferrochrome, ferrocopper, and ferromolybdenum are added, the mixture is stirred for 3 min. The concentrations of Cu, Cr, and Mo are controlled to be 0.18%, 0.25%, and 0.04%. The temperature is lowered to 1580℃, and ferrovanadium and ferrotitanium are added. The mixture is stirred for 2 min at an argon flow rate of 0.5 Nm³ / (min·t). The concentrations of V, Ti, and Ti are controlled to be 0.025% and 0.008%, respectively, to obtain alloyed steel liquid. Step (4): Cool the alloyed steel liquid to 1570℃, use a sealed wire feeder, and protect it with argon gas throughout (argon gas flow rate is 0.3 Nm³ / (min·t)). At the same time, feed in composite rare earth and boron cored wire (supplier: Wuxi Zhenye Xingsheng Metallurgical Materials Technology Co., Ltd., boron-iron cored wire). After the wire feeding is completed, let it stand for 8 minutes, control the N: 0.0060% by bottom blowing nitrogen, and then transfer it to a vacuum chamber. Evacuate to a vacuum degree of 66 Pa and maintain the vacuum for 13 minutes, with argon gas bottom blowing throughout (argon gas flow rate is 0.3 Nm³ / (min·t)). After the vacuum is broken, the molten steel is held at 1590℃ for 8 minutes to obtain refined molten steel. At the same time, the wire feeding speed of composite rare earth and boron cored wire is as follows: 2.0 m / s in the early stage (first 1 / 3 of the length before wire feeding) and 3.0 m / s in the later stage (last 2 / 3 of the length after wire feeding) into the alloyed molten steel. The wire feeding depth is 60% of the depth of the alloyed molten steel, and the wire feeding angle is 15° inclined. The composite rare earth is obtained by mixing La, Ce and Y in a mass ratio of 2:3:1, with composite rare earth: 0.0010% and B: 0.0010%. The outer diameter of the boron cored wire is 13 mm.

[0030] Step (5): The refined molten steel is continuously cast at a temperature of 15°C with a superheat of 15°C. The casting speed is controlled at 1.8 m / min. The electromagnetic stirring of the crystallizer is turned on and stirred for 3 minutes to obtain a continuously cast billet. The continuously cast billet is naturally cooled to 400°C in a closed slow cooling pit, then transferred to the room temperature zone and cooled to room temperature. It is then cut into 6 m billets to obtain a continuously cast steel billet. The crystallizer used for electromagnetic stirring is 0.9 m long and has a stirring frequency of 3 Hz.

[0031] Step (6): Place the continuously cast steel billet in a walking beam furnace and use a three-stage gradient heating process, then perform an integrated process of adaptive controlled rolling-variable pressure water cooling to obtain rolled steel bars; perform temperature-controlled stacking cooling on the rolled steel bars to obtain high-strength earthquake-resistant steel bars.

[0032] The three-stage gradient heating is as follows: Preheating stage: heating to 800℃ within 35 minutes and holding for 10 minutes; Heating stage: heating to 1140℃ within 30 minutes and holding for 20 minutes; Soaking stage: holding at 1150℃ for 50 minutes. The adaptive controlled rolling-variable pressure water cooling integrated process is as follows: (1) Rough rolling and intermediate rolling: the initial rolling temperature is 1030℃ and the total reduction rate is 60%; the temperature of the rough rolling stage is controlled at 990℃ and the temperature of the intermediate rolling stage is controlled at 920℃; (2) Pre-finishing rolling controlled cooling: a first-stage variable pressure water cooling is adopted, the water pressure is 0.7MPa, the length of the cooling section is 4m and the length of the uniform temperature section is 25m, and the temperature of the rolled piece entering the pre-finishing rolling is controlled at 870℃; (3) Finishing rolling: the temperature of the rolled piece entering the finishing rolling is controlled at 840℃, and the total reduction rate is 40%; (4) Final rolling multi-stage controlled cooling: a second-stage variable pressure water cooling is adopted, the water pressure is 1.9MPa, and it is first rapidly cooled to 710℃ at a rate of 20℃ / s, then enters the tempering section and is kept at 690℃ for 5min, and then cooled to 630℃. The temperature-controlled stack cooling process involves placing the rolled steel bars on a cooling bed, first air cooling them to 530°C, and then transferring them to a sealed slow cooling pit for slow cooling to room temperature at a rate of 40°C / h. The entire stack cooling process takes 24 hours.

[0033] Example 2 A high-strength earthquake-resistant steel bar is composed of the following components by weight percentage: C: 0.17%, Si: 0.42%, Mn: 1.32%, V: 0.030%, N: 0.0072%, Cu: 0.21%, Cr: 0.30%, Mo: 0.06%, composite rare earth: 0.014%, B: 0.0015%, Ti: 0.011%, with the remainder being Fe. The impurity content is controlled as follows: P: 0.014%, S: 0.006%, O: 0.0015%. The sum of the weight percentages of all components is 100%.

[0034] A high-strength earthquake-resistant steel bar, the production method of which includes the following specific steps: Step (1): Heat pig iron from room temperature to 1420℃ and hold for 40 minutes to obtain molten iron. Then add desulfurizing agent to the molten iron and stir at 140 rpm for 11 minutes. Let it stand for 6 minutes and remove the top sulfur slag to obtain desulfurized molten iron with S: 0.006%. Add dephosphorizing agent to the desulfurized molten iron and control the temperature at 1340℃. Stir at 140 rpm for 12 minutes by bottom blowing argon (argon flow rate of 0.5 Nm³ / (min·t)). Remove the phosphorus slag to obtain pretreated molten iron with P: 0.016%. The ratio of molten iron to desulfurizing agent is 1t: 19kg. The desulfurizing agent is a mixture of calcium oxide and sodium carbonate in a mass ratio of 6.5: 2.5. The ratio of desulfurized molten iron to dephosphorizing agent is 1t: 9kg. The dephosphorizing agent is a mixture of iron oxide scale, lime, and fluorite in a mass ratio of 3.0: 6: 0.9.

[0035] Step (2): The pretreated molten iron is transferred into the converter at an inlet temperature of 1450℃. The top and bottom blowing process is used for smelting, with oxygen blown from the top and argon blown from the bottom. When the temperature reaches 1650℃, the steel is tapped. During the tapping process, ferromanganese and ferrosilicon are added, and slag is blocked during tapping to obtain primary molten steel. The primary molten steel has the following composition: O: 0.0015%, Mn: 1.32%, Si: 0.42%. The flow rate of top-blown oxygen is controlled at 4.0 Nm³ / (min·t), and the flow rate of bottom-blown argon is controlled at 0.45 Nm³ / (min·t).

[0036] Step (3): The primary molten steel is fed into the LF refining furnace, and argon is blown into the bottom throughout the process (argon flow rate is 0.40 Nm³ / (min·t)). The temperature of the refining furnace is raised to 1620℃, and ferrochrome, ferrocopper, and ferromolybdenum are added in sequence. Each addition of a component is stirred for 5 min, and after all the ferrochrome, ferrocopper, and ferromolybdenum are added, the mixture is stirred for 4 min. The concentrations of Cu: 0.21%, Cr: 0.30%, and Mo: 0.06% are controlled. The temperature is lowered to 1590℃, and ferrovanadium and ferrotitanium are added. The mixture is stirred for 2.5 min at an argon flow rate of 0.55 Nm³ / (min·t) and the concentrations of V: ​​0.030% and Ti: 0.011% are controlled to obtain alloyed steel liquid. Step (4): Cool the alloyed steel liquid to 1580℃, use a sealed wire feeder, and protect it with argon gas throughout (argon gas flow rate is 0.45 Nm³ / (min·t)). At the same time, feed in composite rare earth and boron cored wire (supplier: Wuxi Zhenye Xingsheng Metallurgical Materials Technology Co., Ltd., boron iron cored wire). After the wire feeding is completed, let it stand for 9 minutes, control N: 0.0072% by bottom blowing nitrogen gas, and then transfer it to the vacuum chamber. Evacuate to a vacuum degree of 67 Pa and maintain the vacuum for 14 minutes. Bottom blow argon gas throughout (argon gas flow rate is 0.45 Nm³ / (min·t)). After breaking the vacuum, the molten steel is held at 1605℃ for 10 minutes to obtain refined molten steel. At the same time, the wire feeding speed of composite rare earth and boron cored wire is as follows: 2.3 m / s in the early stage (2 / 5 of the length before wire feeding) and 3.2 m / s in the later stage (3 / 5 of the length after wire feeding) into the alloyed steel liquid. The wire feeding depth is 60% of the depth of the alloyed steel liquid, and the wire feeding angle is 15° inclined. The composite rare earth is La, Ce and Y mixed in a mass ratio of 2.2:3.3:1.2, with composite rare earth content of 0.014% and boron content of 0.0015%. The outer diameter of the boron cored wire is 14 mm.

[0037] Step (5): The refined molten steel is continuously cast at a temperature of 20°C with a superheat of 20°C. The casting speed is controlled at 2.1 m / min. The electromagnetic stirring of the crystallizer is turned on and stirred for 4 min to obtain a continuously cast billet. The continuously cast billet is naturally cooled to 400°C in a closed slow cooling pit, and then transferred to the room temperature zone to continue cooling to room temperature. It is then cut into 9 m billets to obtain a continuously cast steel billet. The crystallizer used for electromagnetic stirring is 1.0 m long and has a stirring frequency of 4 Hz.

[0038] Step (6): Place the continuously cast steel billet in a walking beam furnace and use a three-stage gradient heating process, then perform an integrated process of adaptive controlled rolling-variable pressure water cooling to obtain rolled steel bars; perform temperature-controlled stacking cooling on the rolled steel bars to obtain high-strength earthquake-resistant steel bars.

[0039] The three-stage gradient heating is as follows: Preheating stage: the temperature is raised to 850℃ within 37 minutes and held for 13 minutes; Heating stage: the temperature is raised to 1155℃ within 33 minutes and held for 23 minutes; Soaking stage: the temperature is held at 1160℃ for 55 minutes. The adaptive controlled rolling-variable pressure water cooling integrated process is as follows: (1) Rough rolling and intermediate rolling: the initial rolling temperature is 1045℃ and the total reduction rate is 63%; the temperature of the rough rolling stage is controlled at 1025℃ and the temperature of the intermediate rolling stage is controlled at 955℃; (2) Pre-finishing rolling controlled cooling: a first-stage variable pressure water cooling is adopted, the water pressure is 0.8MPa, the cooling section length is 4m and the uniform temperature section length is 25m, and the temperature of the rolled piece entering the pre-finishing rolling is controlled at 885℃; (3) Finishing rolling: the temperature of the rolled piece entering the finishing rolling is controlled at 850℃, and the total reduction rate is 44%; (4) Final rolling multi-stage controlled cooling: a second-stage variable pressure water cooling is adopted, the water pressure is 2.1MPa, and the temperature is first rapidly cooled to 725℃ at a rate of 20℃ / s, then enters the tempering section and is kept at 700℃ for 10min, and then cooled to 645℃. The temperature-controlled stack cooling process involves placing the rolled steel bars on a cooling bed, first air cooling them to 540℃, and then transferring them to a sealed slow cooling pit for slow cooling to room temperature at a rate of 40℃ / h. The entire stack cooling process takes 30 hours.

[0040] Example 3 A high-strength earthquake-resistant steel bar is composed of the following components by weight percentage: C: 0.19%, Si: 0.50%, Mn: 1.40%, V: 0.035%, N: 0.0085%, Cu: 0.25%, Cr: 0.35%, Mo: 0.08%, composite rare earth: 0.018%, B: 0.0020%, Ti: 0.015%, with the remainder being Fe. The impurity content is controlled as follows: P: 0.014%, S: 0.005%, O: 0.0013%. The sum of the weight percentages of all components is 100%.

[0041] A high-strength earthquake-resistant steel bar, the production method of which includes the following specific steps: Step (1): Heat pig iron from room temperature to 1450℃ and hold for 50 minutes to obtain molten iron. Then add desulfurizing agent to the molten iron and stir at 150 rpm for 12 minutes. Let it stand for 7 minutes and remove the top sulfur slag to obtain desulfurized molten iron with S: 0.005%. Add dephosphorizing agent to the desulfurized molten iron and control the temperature at 1380℃. Stir at 150 rpm for 12 minutes by bottom blowing argon (argon flow rate of 0.6 Nm³ / (min·t)). Remove the phosphorus slag to obtain pretreated molten iron with P: 0.014%. The ratio of molten iron to desulfurizing agent is 1t: 20kg. The desulfurizing agent is a mixture of calcium oxide and sodium carbonate in a mass ratio of 7:3. The ratio of desulfurized molten iron to dephosphorizing agent is 1t: 10kg. The dephosphorizing agent is a mixture of iron oxide scale, lime, and fluorite in a mass ratio of 3.5: 7: 1.0.

[0042] Step (2): The pretreated molten iron is transferred into the converter at a temperature of 1500℃. The top and bottom blowing process is used for smelting, with oxygen blown from the top and argon blown from the bottom. When the temperature reaches 1660℃, the steel is tapped. During the tapping process, ferromanganese and ferrosilicon are added, and slag is blocked during tapping to obtain primary molten steel. The primary molten steel has the following composition: O: 0.0013%, Mn: 1.40%, Si: 0.50%. The flow rate of top-blown oxygen is controlled at 4.5 Nm³ / (min·t), and the flow rate of bottom-blown argon is controlled at 0.6 Nm³ / (min·t).

[0043] Step (3): The primary molten steel is fed into the LF refining furnace, and argon is blown into the bottom throughout the process (argon flow rate is 0.48 Nm³ / (min·t)). The temperature of the refining furnace is raised to 1630℃, and ferrochrome, ferrocopper, and ferromolybdenum are added in sequence. Each addition of a component is stirred for 6 min, and after all the ferrochrome, ferrocopper, and ferromolybdenum are added, the mixture is stirred for 5 min. The concentrations of Cu: 0.25%, Cr: 0.35%, and Mo: 0.08% are controlled. The temperature is lowered to 1600℃, and ferrovanadium and ferrotitanium are added. The mixture is stirred for 3 min at an argon flow rate of 0.6 Nm³ / (min·t). The concentrations of V: ​​0.035% and Ti: 0.015% are controlled to obtain alloyed steel liquid. Step (4): Cool the alloyed steel liquid to 1590℃, use a sealed wire feeder, and protect it with argon gas throughout (argon gas flow rate is 0.6 Nm³ / (min·t)). Simultaneously feed in composite rare earth and boron cored wire (supplier: Wuxi Zhenye Xingsheng Metallurgical Materials Technology Co., Ltd., boron-iron cored wire). After feeding, let it stand for 10 minutes, then bottom-purge with nitrogen to control N: 0.0085%, and then transfer it to a vacuum chamber. Evacuate to a vacuum degree of 67 Pa and maintain the vacuum for 15 minutes, bottom-purge with argon gas throughout (argon gas flow rate is 0.6 Nm³ / (min·t)). After vacuuming, the molten steel is held at 1620℃ for 12 minutes to obtain refined molten steel. At the same time, the wire feeding speed of composite rare earth and boron cored wire is as follows: 2.5 m / s in the early stage (first 1 / 2 length before wire feeding) and 3.5 m / s in the later stage (last 1 / 2 length after wire feeding) into the alloyed molten steel. The wire feeding depth is 60% of the depth of the alloyed molten steel, and the wire feeding angle is 15° inclined. The composite rare earth is La, Ce and Y mixed in a mass ratio of 2.5:3.5:1.5, with composite rare earth content of 0.018% and boron content of 0.0020%. The outer diameter of the boron cored wire is 16 mm.

[0044] Step (5): The refined molten steel is continuously cast at a temperature of 25°C with a superheat of 25°C. The casting speed is controlled at 2.4 m / min. The electromagnetic stirring of the crystallizer is turned on and stirred for 5 minutes to obtain a continuously cast billet. The continuously cast billet is naturally cooled to 400°C in a closed slow cooling pit, and then transferred to the room temperature zone to continue cooling to room temperature. It is then cut into 12 m billets to obtain a continuously cast steel billet. The crystallizer used for electromagnetic stirring is 1.2 m long and has a stirring frequency of 5 Hz.

[0045] Step (6): Place the continuously cast steel billet in a walking beam furnace and use a three-stage gradient heating process, then perform an integrated process of adaptive controlled rolling-variable pressure water cooling to obtain rolled steel bars; perform temperature-controlled stacking cooling on the rolled steel bars to obtain high-strength earthquake-resistant steel bars.

[0046] The three-stage gradient heating is as follows: Preheating stage: heating to 900℃ within 40 minutes and holding for 15 minutes; Heating stage: heating to 1170℃ within 35 minutes and holding for 25 minutes; Soaking stage: holding at 1170℃ for 60 minutes. The adaptive controlled rolling-variable pressure water cooling integrated process is as follows: (1) Rough rolling and intermediate rolling: the initial rolling temperature is 1060℃ and the total reduction rate is 65%; the temperature of the rough rolling stage is controlled at 1040℃ and the temperature of the intermediate rolling stage is controlled at 990℃; (2) Pre-finishing rolling controlled cooling: a first-stage variable pressure water cooling is adopted, the water pressure is 0.9MPa, the cooling section length is 4m and the uniform temperature section length is 25m, and the temperature of the rolled piece entering the pre-finishing rolling is controlled at 900℃; (3) Finishing rolling: the temperature of the rolled piece entering the finishing rolling is controlled at 860℃, and the total reduction rate is 48%; (4) Final rolling multi-stage controlled cooling: a second-stage variable pressure water cooling is adopted, the water pressure is 2.3MPa, and it is first rapidly cooled to 740℃ at a rate of 20℃ / s, then enters the tempering section and is kept at 710℃ for 15min, and then cooled to 660℃. The temperature-controlled stack cooling process involves placing the rolled steel bars on a cooling bed, first air cooling them to 550°C, and then transferring them to a sealed slow cooling pit for slow cooling to room temperature at a rate of 40°C / h. The entire stack cooling process takes 36 hours.

[0047] Comparative Example 1 Compared with Example 3, in the process of preparing high-strength earthquake-resistant steel bars, the alloying steel liquid in step (3) is replaced with alloying steel liquid-1, and the rest is exactly the same as in Example 3, and high-strength earthquake-resistant steel bars are obtained. The preparation of alloyed steel liquid-1 is as follows: the primary molten steel is fed into the LF refining furnace, and argon gas is blown into the bottom throughout the process (flow rate of 0.48 Nm³ / (min·t)). The temperature of the refining furnace is raised to 1630℃, and ferrochrome, ferrocopper, ferromolybdenum, ferrovanadium, and ferrotitanium are added to it in sequence. Each component is stirred for 6 min after being added, and after all the components are added, the mixture is stirred for 8 min. The proportions of Cu: 0.25%, Cr: 0.35%, Mo: 0.08%, V: 0.035%, and Ti: 0.015% are controlled to obtain alloyed steel liquid-1.

[0048] Comparative Example 2 Compared with Example 3, in the process of preparing high-strength earthquake-resistant steel bars, the wire feeding speed in step (4) is controlled to 2.5 m / s throughout the process, and the rest is exactly the same as in Example 3, so as to obtain high-strength earthquake-resistant steel bars.

[0049] Comparative Example 3 Compared with Example 3, in the preparation process of high-strength earthquake-resistant steel bars, the three-stage gradient heating in step (6) is replaced with one-stage heating: the temperature is raised to 1170℃ within 75 minutes and held for 60 minutes, and the rest is exactly the same as in Example 3, so as to obtain high-strength earthquake-resistant steel bars.

[0050] Comparative Example 4 Compared with Example 3, in the preparation process of high-strength earthquake-resistant steel bars, the final rolling multi-stage controlled cooling in step (6) was replaced by direct rapid cooling to 660°C under a water pressure of 2.3 MPa. The rest was exactly the same as in Example 3, and high-strength earthquake-resistant steel bars were obtained.

[0051] Comparative Example 5 Compared with Example 3, in the process of preparing high-strength earthquake-resistant steel bars, the rolled steel bars in step (6) are placed directly in a sealed slow cooling pit and cooled to room temperature. The rest is exactly the same as in Example 3, and high-strength earthquake-resistant steel bars are obtained.

[0052] The high-strength earthquake-resistant steel bars prepared in Examples 1-3 and Comparative Examples 1-5 of the present invention were further tested below, and the test results are shown below.

[0053] The mechanical properties of the steel bars (including yield strength, tensile strength, elongation after fracture, total elongation at maximum force and yield strength ratio) were tested in accordance with GB 1499.2-2024 "Steel for reinforced concrete - Part 2: Hot-rolled ribbed steel bars".

[0054] Referring to the method of GB / T 10125-2012 "Salt spray test for corrosion in artificial atmosphere", a 96-hour salt spray test was conducted. The corrosion resistance of the steel bars was evaluated by relative corrosion degree in accordance with GB / T 6461-2002 "Rating of specimens and test pieces of metal and other inorganic coatings on metal substrates after corrosion test".

[0055] The results are recorded in Table 1; Table 1: Test Results of High-Strength Seismic Reinforcement According to the data in Table 1, the high-strength earthquake-resistant steel bars prepared by the present invention have good mechanical properties and corrosion resistance. In particular, the elongation after fracture and the total elongation at maximum force are significantly improved, which meets the requirements of strength, toughness and high ductility of earthquake-resistant steel bars.

[0056] Comparing Example 3 with Comparative Example 1, it can be seen that in the process of preparing high-strength earthquake-resistant steel bars, replacing the alloyed steel liquid in step (3) with alloyed steel liquid-1 indicates that the high-strength earthquake-resistant steel bars prepared by the present invention using alloyed steel liquid have better mechanical properties and corrosion resistance.

[0057] Comparing Example 3 with Comparative Example 2, it can be seen that in the process of preparing high-strength earthquake-resistant steel bars, the wire feeding speed in step (4) is controlled to 2.5 m / s throughout the process. This shows that the high-strength earthquake-resistant steel bars prepared by the variable-speed wire feeding technology of the present invention, which involves "low-speed furnace entry in the early stage and high-speed deep burial in the later stage", have better mechanical properties and corrosion resistance.

[0058] Comparing Example 3 with Comparative Example 3, it can be seen that in the process of preparing high-strength earthquake-resistant steel bars, the three-stage gradient heating in step (6) is replaced with one-stage heating: the temperature is raised to 1170℃ within 75 minutes and held for 60 minutes. It is evident that the high-strength earthquake-resistant steel bars prepared by the three-stage gradient heating method of the present invention have better corrosion resistance and better mechanical properties.

[0059] Comparing Example 3 with Comparative Example 4, it can be seen that in the process of preparing high-strength earthquake-resistant steel bars, replacing the final rolling multi-stage controlled cooling in step (6) with direct rapid cooling to 660°C under a water pressure of 2.3 MPa, the high-strength earthquake-resistant steel bars prepared by the present invention through final rolling multi-stage controlled cooling have better corrosion resistance and better mechanical properties.

[0060] Comparing Example 3 with Comparative Example 5, it can be seen that in the process of preparing high-strength earthquake-resistant steel bars, the steel bars rolled in step (6) are placed directly in a sealed slow cooling pit and cooled to room temperature. This shows that the high-strength earthquake-resistant steel bars prepared by the present invention through temperature-controlled stacking and cooling of rolled steel bars have better mechanical properties.

[0061] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A high-strength earthquake-resistant steel bar, characterized in that: The composition, by weight percentage, consists of the following components: C: 0.16-0.19%, Si: 0.35-0.50%, Mn: 1.25-1.40%, V: 0.025-0.035%, N: 0.0060-0.0085%, Cu: 0.18-0.25%, Cr: 0.25-0.35%, Mo: 0.04-0.08%, composite rare earth: 0.010-0.018%, B: 0.0010-0.0020%, Ti: 0.008-0.015%, with the remainder being Fe. Impurity content is controlled as follows: P≤0.020%, S≤0.008%, O≤0.0020%. The sum of the weight percentages of all components is 100%.

2. The high-strength earthquake-resistant steel bar according to claim 1, characterized in that: The production method of the high-strength earthquake-resistant steel bars includes the following steps: Step (1): Heat pig iron to obtain molten iron, then add desulfurizing agent to molten iron, stir, let stand, remove the sulfur slag on top to obtain desulfurized molten iron; add dephosphorizing agent to desulfurized molten iron, control the temperature, blow argon gas from the bottom, and then remove phosphorus slag to obtain pretreated molten iron. Step (2): The pretreated molten iron is transferred into the converter and smelted using a top and bottom blowing process. Oxygen is blown from the top and argon is blown from the bottom. During the tapping process, ferromanganese and ferrosilicon are added, and slag is blocked during tapping to obtain primary molten steel. Step (3): The primary molten steel is fed into the LF refining furnace, and argon gas is blown from the bottom throughout the process. The refining furnace is heated up, and ferrochrome, ferrocopper, and ferromolybdenum are added to it in sequence and stirred and mixed. The temperature is lowered, and ferrovanadium and ferrotitanium are added and stirred to obtain alloyed molten steel. Step (4): Cool the alloyed steel liquid, use a sealed wire feeder, argon gas protection throughout the process, feed composite rare earth and boron cored wire at the same time, after the wire feeding is completed, let it stand, blow nitrogen gas from the bottom, and then transfer it to the vacuum chamber for degassing. After breaking the vacuum, keep it at the temperature to obtain refined molten steel. Step (5): The refined molten steel is continuously cast, the casting speed is controlled, and the electromagnetic stirring of the crystallizer is turned on to obtain the continuously cast billet; after the continuously cast billet is naturally cooled on the sealed slow cooling pit, it is transferred to the room temperature area and cooled to room temperature, and then cut into steel billets to obtain the continuously cast steel billet. Step (6): Place the continuously cast steel billet in a walking beam furnace and use a three-stage gradient heating process, then perform an integrated process of adaptive controlled rolling-variable pressure water cooling to obtain rolled steel bars; perform temperature-controlled stacking cooling on the rolled steel bars to obtain high-strength earthquake-resistant steel bars.

3. The high-strength earthquake-resistant steel bar according to claim 2, characterized in that: In step (1), the ratio of molten iron to desulfurizing agent is 1t: 18-20kg; the ratio of desulfurized molten iron to dephosphorizing agent is 1t: 8-10kg.

4. The high-strength earthquake-resistant steel bar according to claim 2, characterized in that: In step (2), the flow rate of the top-blown oxygen is controlled at 3.5-4.5 Nm³ / (min·t), and the flow rate of the bottom-blown argon is controlled at 0.3-0.6 Nm³ / (min·t).

5. A high-strength earthquake-resistant steel bar according to claim 2, characterized in that: In step (4), the wire feeding speed of simultaneously feeding composite rare earth and boron cored wire is: 2.0-2.5 m / s into the furnace in the early stage, and 3.0-3.5 m / s into the alloyed steel liquid in the later stage. The wire feeding depth is 60% of the depth of the alloyed steel liquid, the wire feeding angle is ≤15° inclined, and the outer diameter of the boron cored wire is 13-16 mm.

6. The high-strength earthquake-resistant steel bar according to claim 2, characterized in that: In step (5), the crystallizer used for electromagnetic stirring of the crystallizer has a length of 0.9-1.2m and a stirring frequency of 3-5Hz.

7. A high-strength earthquake-resistant steel bar according to claim 2, characterized in that: In step (6), the three-stage gradient heating is as follows: preheating stage: heating to 800-900℃ within 35-40 min and holding for 10-15 min; heating stage: heating to 1140-1170℃ within 30-35 min and holding for 20-25 min; and heat equalization stage: holding for 50-60 min at 1150-1170℃.

8. A high-strength earthquake-resistant steel bar according to claim 2, characterized in that: In step (6), the adaptive controlled rolling-variable pressure water cooling integrated process is as follows: (1) Rough rolling and intermediate rolling: The initial rolling temperature is 1030-1060℃, and the total reduction rate is 60-65%; the temperature of the rough rolling stage is controlled at 990-1040℃, and the temperature of the intermediate rolling stage is controlled at 920-990℃. (2) Pre-finishing rolling controlled cooling: a single-stage variable pressure water cooling system is adopted, with a water pressure of 0.7-0.9MPa, a cooling section length of 4m, a uniform temperature section length of 25m, and the temperature of the rolled piece entering the pre-finishing rolling mill is controlled at 870-900℃; (3) Finishing rolling: The temperature of the rolled piece entering the finishing rolling mill is controlled at 840-860℃, and the total reduction rate is 40-48%; (4) Final rolling multi-stage controlled cooling: Two-stage variable pressure water cooling is adopted, with a water pressure of 1.9-2.3MPa. First, it is cooled to 710-740℃, then enters the tempering section and is held at 690-710℃ for 5-15 minutes, and then cooled to 630-660℃.

9. A high-strength earthquake-resistant steel bar according to claim 2, characterized in that: In step (6), the temperature-controlled stacking cooling is as follows: the rolled steel bar is placed on a cooling bed and first air-cooled to 530-550℃, and then transferred to a sealed slow cooling pit and slowly cooled to room temperature at a rate of ≤40℃ / h. The total stacking cooling time is 24-36h.

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