Preparation method of low-yield-ratio and high-strength steel plate for building structure

Abstract

The invention relates to the technical field of steel preparation, and provides a preparation method of a low-yield-ratio high-strength steel plate for a building structure, which comprises the steps of converter smelting, LF refining, RH vacuum degassing, continuous casting, slab stack cooling, heating and rolling. In the rolling process, rough rolling complete recrystallization rolling is adopted, and finish rolling non-recrystallization area rolling is adopted. According to the technical scheme, the problem that the yield strength of the steel plate for the building structure is high in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of steel preparation technology, specifically to a method for preparing a high-strength steel plate for building structures with a low yield strength ratio. Background Technology

[0002] Structural steel is widely used in high-rise and super high-rise buildings, such as large stadiums, high-speed rail stations, super high-rise commercial buildings, and office buildings. Due to the seismic resistance requirements of structural steel, these products often need to have a low yield-to-tensile strength ratio to ensure the safety and reliability of the material structure. The yield-to-tensile strength ratio of structural steel should generally be ≤0.85. Under dynamic loads such as earthquakes, the structure needs to absorb energy through the plastic deformation of the steel. However, steel with a high yield-to-tensile strength ratio is prone to rapidly entering the strengthening stage and fracturing after reaching its yield strength, resulting in insufficient plastic deformation capacity and potentially leading to sudden structural failure, thus failing to meet the seismic resistance performance requirements of structural steel. In addition, structural steel should possess good mechanical properties and adequate impact toughness.

[0003] As market demands for structural steel continue to rise, the manufacturing processes for structural steel are also constantly evolving. Currently, by accelerating the cooling rate after rolling, not only can grain growth be suppressed, but also the ultrafine ferrite or bainite microstructure required for high strength and toughness can be obtained, achieving phase transformation and resulting in a high-strength, high-toughness microstructure. However, the most significant characteristic of this microstructure is that the yield strength increases too rapidly compared to the tensile strength, resulting in a high yield-to-tensile ratio, which makes structural steel unable to effectively meet the requirements for safety and earthquake resistance.

[0004] Based on this, a method for preparing high-strength steel plates for building structures with low yield strength ratio is proposed. By optimizing the rolling process, the yield strength ratio of the steel plates for building structures can be effectively reduced, and they can have good mechanical properties. This is of great significance for meeting the performance requirements of steel for building structures in terms of safety and seismic resistance. Summary of the Invention

[0005] This invention proposes a method for preparing high-strength steel plates for building structures with low yield strength ratio, which solves the problem of high yield strength ratio in steel plates for building structures in related technologies.

[0006] The technical solution of the present invention is as follows: This invention proposes a method for preparing a low yield strength ratio high strength building structural steel plate, including converter smelting, LF refining, RH vacuum degassing, continuous casting, slab stack cooling, heating, and rolling; During the rolling process, rough rolling for complete recrystallization and finish rolling for the non-recrystallization zone are employed. When the thickness of the rolled steel plate is 8mm≤10mm≤, the thickness of the intermediate billet is ≥35mm, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 980~1000℃, and the final rolling temperature is ≤810℃. When 10mm < the thickness of the rolled steel plate ≤ 14mm, the thickness of the intermediate billet ≥ 40mm, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 930~950℃, and the final rolling temperature is ≤ 810℃. When 14mm < the thickness of the rolled steel plate ≤ 16mm, the thickness of the intermediate billet ≥ 55mm, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 910~930℃, and the final rolling temperature is ≤ 810℃. When 16mm < the thickness of the rolled steel plate ≤ 30mm, the thickness of the intermediate billet ≥ 3t, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 860~880℃, and the final rolling temperature is ≤ 800℃. When 30mm < rolled steel plate thickness ≤ 40mm, the intermediate billet thickness ≥ 2.5t, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 830~850℃, and the final rolling temperature is ≤ 790℃. When 40mm < the thickness of the rolled steel plate ≤ 50mm, the thickness of the intermediate billet ≥ 2t, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 810~830℃, and the final rolling temperature is ≤ 790℃. When 50mm < the thickness of the rolled steel plate ≤ 60mm, the thickness of the intermediate billet ≥ 120mm, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 800~820℃, and the final rolling temperature is ≤ 790℃.

[0007] As a further technical solution, the steel plate is composed of the following components by weight percentage: C 0.16%~0.19%, Si 0.20%~0.45%, Mn 1.40%~1.50%, P≤0.018%, S≤0.005%, Nb0.020%~0.030%, V 0.065%~0.080%, N 0.0090%~0.014%, with the balance being iron and its unavoidable impurities.

[0008] As a further technical solution, the temperature during the rough rolling process of full recrystallization is 1000~1100℃, and the total reduction rate is >60%.

[0009] As a further technical solution, the heating process can be carried out using either dual-furnace heating or triple-furnace heating.

[0010] As a further technical solution, during the heating process, the temperature of the heating section is 1180~1260℃, the temperature of the soaking section is 1210~1250℃, the total furnace time is 10~13min / cm, and the sum of the furnace time of the heating section and the soaking section is 40%~50% of the total furnace time.

[0011] As a further technical solution, during the RH vacuum degassing process, the bottom blowing of the RH furnace is switched from argon to nitrogen, and nitrogen is blown throughout the process to increase N, controlling the nitrogen content to be 0.0090%~0.014%.

[0012] As a further technical solution, the converter smelting has a slag basicity of 2.8~3.0, an end temperature of 1630~1680℃, and a post-furnace temperature of 1550~1570℃.

[0013] As a further technical solution, during the RH vacuum degassing process, the pure vacuum treatment time is ≥15min.

[0014] As a further technical solution, the superheat during continuous casting is 15~25℃.

[0015] As a further technical solution, when the thickness of the rolled steel plate is 16mm or less and 60mm or less, the rolling process includes ultra-rapid cooling, with an initial cooling temperature of 740~790℃ and a cooling rate of 6~10℃ / s.

[0016] As a further technical solution, when the thickness of the rolled steel plate is 40mm or less and 60mm or less, the ultra-rapid cooling also includes stacking cooling of the steel plate.

[0017] As a further technical solution, when the steel plate is stacked and cooled, the stacking temperature is 350~550℃ and the stacking time is 48h.

[0018] The working principle and beneficial effects of this invention are as follows: In this invention, by strictly controlling the rolling process, a rolling method combining rough rolling for complete recrystallization and finishing rolling for the non-recrystallization zone is adopted to produce Q420GJC high-strength structural steel plates. The initial rolling temperature and final rolling temperature during the two-stage finishing rolling for different steel plate thicknesses are rationally adjusted. When the steel plate thickness after rolling is 8mm ≤ 10mm, the initial rolling temperature during finishing rolling for the non-recrystallization zone is 980~1000℃, and the final rolling temperature is ≤ 800℃. 10℃; When 10mm < rolled steel plate thickness ≤ 14mm, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 930~950℃, and the final rolling temperature is ≤ 810℃; When 14mm < rolled steel plate thickness ≤ 16mm, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 910~930℃, and the final rolling temperature is ≤ 810℃; When 16mm < rolled steel plate thickness ≤ 30mm, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 860℃. ~880℃, final rolling temperature ≤800℃; when 30mm < rolled steel plate thickness ≤40mm, the initial rolling temperature in the non-recrystallization zone of the finishing roll is 830~850℃, and the final rolling temperature ≤790℃; when 40mm < rolled steel plate thickness ≤50mm, the initial rolling temperature in the non-recrystallization zone of the finishing roll is 810~830℃, and the final rolling temperature ≤790℃; when 50mm < rolled steel plate thickness ≤60mm, the final rolling temperature in the non-recrystallization zone of the finishing roll is 810~830℃, and the final rolling temperature ≤790℃. The initial rolling temperature during zone rolling is 800~820℃, and the final rolling temperature is ≤790℃. It can optimize the internal structure of steel plates with different target thicknesses to obtain a uniform structure with high strength and high toughness, which can improve the mechanical properties of steel plates for building structures. It also has a low yield strength ratio, which is less than 0.75, with an average of 0.73. This is 0.12 lower than the standard requirement of 0.85, and fully meets the safety and seismic resistance requirements of Q420GJC steel for building structures. Attached Figure Description

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 The image shows the metallographic structure at 1 / 4 of the low yield strength ratio high strength building structure steel plate prepared in Example 10. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 A method for preparing a low yield strength ratio, high strength steel plate for building structures includes the following steps: S1. Molten iron is smelted in a converter, refined in an LF furnace, degassed in an RH furnace under vacuum, and continuously cast to form slabs. During converter smelting, the slag basicity is controlled at 2.8, the final temperature of converter smelting is 1630℃, and the temperature after the furnace is 1550℃. During RH vacuum degassed, the pure vacuum treatment time is 15 minutes, and the RH furnace bottom blowing is switched from argon to nitrogen. Nitrogen is blown throughout the process to increase nitrogen content, and the nitrogen content of the slab is controlled at 0.0090%. During continuous casting, the superheat is controlled at 15℃. S2. The slab is cooled, heated and rolled to obtain a high-strength steel plate for building structures with a low yield strength ratio. During heating, a dual-furnace heating system is used, with the heating section temperature at 1250℃ and the soaking section temperature at 1230℃. The total furnace time is 10 min / cm, and the sum of the furnace time in the heating section and the soaking section accounts for 40% of the total furnace time. During rolling, the original slab thickness is 220mm. First, it is subjected to rough rolling for complete recrystallization at a temperature of 1000℃ and a total reduction of 83%. Then, during the finishing rolling in the non-recrystallization zone, the initial rolling temperature is 980℃ and the final rolling temperature is 810℃. The intermediate slab thickness is 35mm during the finishing rolling in the non-recrystallization zone. After rolling, it is air-cooled to finally obtain a low yield strength ratio high strength building structure steel plate with a thickness of 8mm. The steel plate is composed of the following components by weight percentage: C 0.175%, Si 0.30%, Mn 1.45%, P 0.015%, S 0.003%, Nb 0.025%, V 0.075%, N 0.0090%, with the balance being iron and its unavoidable impurities.

[0023] Example 2 A method for preparing a low yield strength ratio, high strength steel plate for building structures includes the following steps: S1. Molten iron is smelted in a converter, refined in an LF furnace, degassed in an RH furnace under vacuum, and continuously cast to form slabs. During converter smelting, the slag basicity is controlled at 3.0, the final temperature of converter smelting is 1680℃, and the temperature after the furnace is 1570℃. During RH vacuum degassed, the pure vacuum treatment time is 20 minutes, and the RH furnace bottom blowing is switched from argon to nitrogen. Nitrogen is blown throughout the process to increase nitrogen content, and the nitrogen content of the slab is controlled at 0.014%. During continuous casting, the superheat is controlled at 25℃. S2. The slab is cooled, heated and rolled to obtain a high-strength steel plate for building structures with a low yield strength ratio. During heating, a dual-furnace heating system is used, with the heating section temperature at 1260℃ and the soaking section temperature at 1250℃. The total furnace time is 13 min / cm, and the sum of the furnace time in the heating section and the soaking section accounts for 45% of the total furnace time. During rolling, the original slab thickness is 220mm. First, it is subjected to rough rolling for complete recrystallization at a temperature of 1100℃ and a total reduction of 81%. Then, it is subjected to finishing rolling in the non-recrystallization zone at an initial rolling temperature of 1000℃ and a final rolling temperature of 800℃. The intermediate slab thickness is 40mm during the finishing rolling in the non-recrystallization zone. After rolling, it is air-cooled to finally obtain a 10mm thick steel plate for building structures with low yield strength ratio. The steel plate is composed of the following components by weight percentage: C 0.18%, Si 0.20%, Mn 1.40%, 0.018%, S 0.005%, Nb 0.020%, V 0.065%, N 0.0140%, with the balance being iron and its unavoidable impurities.

[0024] Example 3 The only difference between this embodiment and Embodiment 1 is that, in this embodiment, when rolling the non-recrystallized zone in the finishing rolling process, the initial rolling temperature is 930℃, the final rolling temperature is 810℃, the intermediate billet thickness is 40mm during the finishing rolling process in the non-recrystallized zone, and the billet is air-cooled after rolling to finally obtain a low yield strength ratio high strength building structure steel plate with a thickness of 12mm. The steel plate is composed of the following components by weight percentage: C 0.19%, Si 0.35%, Mn 1.50%, P 0.01%, S 0.002%, Nb 0.030%, V 0.080%, N 0.013%, with the balance being iron and its unavoidable impurities.

[0025] Example 4 The only difference between this embodiment and Embodiment 1 is that, in this embodiment, during the finishing rolling of the non-recrystallized zone, the initial rolling temperature is 950℃, the final rolling temperature is 800℃, the intermediate billet thickness is 45mm during the finishing rolling of the non-recrystallized zone, and after rolling, it is air-cooled to finally obtain a low yield strength ratio high strength building structure steel plate with a thickness of 14mm.

[0026] Example 5 A method for preparing a low yield strength ratio, high strength steel plate for building structures includes the following steps: S1. Molten steel is smelted in a converter, refined in an LF furnace, degassed in an RH furnace under vacuum, and continuously cast to form slabs. During converter smelting, the slag basicity is controlled at 2.8, the final temperature of converter smelting is 1630℃, and the temperature after the furnace is 1550℃. During RH vacuum degassed, the pure vacuum treatment time is 15 minutes, and the RH furnace bottom blowing is switched from argon to nitrogen. Nitrogen is blown throughout the process to increase nitrogen content, and the nitrogen content of the slab is controlled at 0.0090%. During continuous casting, the superheat is controlled at 21℃. S2. The slab is subjected to slab stacking cooling, heating, rolling, and ultra-rapid cooling to obtain a high-strength steel plate for building structures with a low yield strength ratio. During heating, a dual-furnace heating system is used, with the heating section temperature at 1230℃ and the soaking section temperature at 1220℃. The total furnace time is 10 min / cm, and the sum of the furnace time in the heating section and the soaking section accounts for 40% of the total furnace time. During rolling, rough rolling with full recrystallization is first used at a temperature of 1000℃ and a total reduction of 74%. Then, finish rolling is performed in the non-recrystallization zone at an initial rolling temperature of 930℃ and a final rolling temperature of 800℃. The intermediate billet thickness is 55mm during the finish rolling process in the non-recrystallization zone. After rolling, the billet is air-cooled to finally obtain a 16mm thick steel plate for building structures with a low yield strength ratio. The steel plate is composed of the following components by weight percentage: C 0.185%, Si 0.30%, Mn 1.45%, P 0.015%, S 0.003%, Nb 0.025%, V 0.075%, N 0.0090%, with the balance being iron and its unavoidable impurities.

[0027] Example 6 A method for preparing a low yield strength ratio, high strength steel plate for building structures includes the following steps: S1. Molten iron is smelted in a converter, refined in an LF furnace, degassed in an RH furnace under vacuum, and continuously cast to form slabs. During converter smelting, the slag basicity is controlled at 2.8, the final temperature of converter smelting is 1630℃, and the temperature after the furnace is 1550℃. During RH vacuum degassed, the vacuum treatment time is 15 minutes, and the RH furnace bottom blowing is switched from argon to nitrogen. Nitrogen is blown throughout the process to increase nitrogen content, and the nitrogen content of the slab is controlled at 0.0090%. During continuous casting, the superheat is controlled at 23℃. S2. The slab is subjected to slab stacking cooling, heating, rolling, and ultra-rapid cooling to obtain a high-strength steel plate for building structures with a low yield strength ratio. During heating, a dual-furnace heating system is used, with the heating section temperature at 1220℃ and the soaking section temperature at 1210℃. The total furnace time is 10 min / cm, and the sum of the furnace time in the heating section and the soaking section accounts for 40% of the total furnace time. During rolling, a rough rolling process with full recrystallization is first adopted, with a rough rolling temperature of 1000℃ and a total reduction rate of 68.8%. Then, a two-stage rolling process is carried out in the non-recrystallization zone of the finish rolling, with an initial rolling temperature of 860℃ and a final rolling temperature of 800℃. During the finish rolling process in the non-recrystallization zone, the thickness of the intermediate billet is 84mm. After rolling, ultra-fast cooling is performed from 790℃ at a cooling rate of 6℃ / s until it reaches 690℃, finally obtaining a 28mm thick steel plate for building structures with low yield strength ratio. The steel plate is composed of the following components by weight percentage: C 0.185%, Si 0.30%, Mn 1.45%, P 0.015%, S 0.003%, Nb 0.025%, V 0.075%, N 0.0090%, with the balance being iron and its unavoidable impurities.

[0028] Example 7 The only difference between this embodiment and embodiment 5 is that in this embodiment, during the two-stage rolling of the non-recrystallized zone, the initial rolling temperature is 880℃, the final rolling temperature is 790℃, the intermediate billet thickness is 90mm during the two-stage rolling of the non-recrystallized zone, and after rolling, ultra-fast cooling is used to accelerate cooling to 685℃, finally obtaining a 30mm thick steel plate for building structures with low yield strength ratio.

[0029] Example 8 The only difference between this embodiment and embodiment 5 is that in this embodiment, during the two-stage rolling of the non-recrystallized zone, the initial rolling temperature is 830°C, the final rolling temperature is 790°C, the intermediate billet thickness is 87.5mm during the two-stage rolling of the non-recrystallized zone, and after rolling, ultra-fast cooling is used to accelerate the cooling to 688°C, finally obtaining a 35mm thick steel plate for building structures with low yield strength ratio.

[0030] Example 9 A method for preparing a low yield strength ratio, high strength steel plate for building structures includes the following steps: S1. Molten iron is smelted in a converter, refined in an LF furnace, degassed in an RH furnace under vacuum, and continuously cast to form slabs. During converter smelting, the slag basicity is controlled at 2.8, the final temperature of converter smelting is 1630℃, and the temperature after the furnace is 1550℃. During RH vacuum degassed, the vacuum treatment time is 18 minutes, and the bottom blowing in the RH furnace is switched from argon to nitrogen. Nitrogen is blown throughout the process to increase nitrogen content, and the nitrogen content of the slab is controlled at 0.0090%. During continuous casting, the superheat is controlled at 23℃. S2. The slab is subjected to slab stacking cooling, heating, rolling, ultra-rapid cooling, and steel plate stacking cooling to obtain a low yield strength ratio high strength steel plate for building structures; During heating, a dual-furnace heating system is used, with the heating section temperature at 1240℃ and the soaking section temperature at 1220℃. The total furnace time is 10 min / cm, and the sum of the furnace time in the heating section and the soaking section accounts for 40% of the total furnace time. During rolling, rough rolling with full recrystallization is first used. The rough rolling temperature is 1000℃ and the total reduction rate is 63%. Then, the non-recrystallization zone is rolled in the finish rolling. The initial rolling temperature is 850℃ and the final rolling temperature is 780℃. The thickness of the intermediate billet during the finish rolling in the non-recrystallization zone is 104mm. After rolling, it is ultra-fast cooled from 790℃ to 685℃ at a cooling rate of 9℃ / s and stacked for 48 hours to finally obtain a 40mm thick steel plate with low yield strength ratio and high strength for building structures. The steel plate is composed of the following components by weight percentage: C 0.185%, Si 0.30%, Mn 1.45%, P 0.015%, S 0.003%, Nb 0.025%, V 0.075%, N 0.0090%, with the balance being iron and its unavoidable impurities.

[0031] Example 10 A method for preparing a low yield strength ratio, high strength steel plate for building structures includes the following steps: S1. Molten iron is smelted in a converter, refined in an LF furnace, degassed in an RH furnace under vacuum, and continuously cast to form slabs. During converter smelting, the slag basicity is controlled at 2.8, the final temperature of converter smelting is 1630℃, and the temperature after the furnace is 1550℃. During RH vacuum degassed, the vacuum treatment time is 15 minutes, and the RH furnace bottom blowing is switched from argon to nitrogen. Nitrogen is blown throughout the process to increase nitrogen content, and the nitrogen content of the slab is controlled at 0.0090%. During continuous casting, the superheat is controlled at 23℃. S2. The slab is subjected to slab stacking cooling, heating, rolling, ultra-rapid cooling, and steel plate stacking cooling to obtain a low yield strength ratio high strength steel plate for building structures; During heating, a dual-furnace heating system is used, with the heating section temperature at 1236℃ and the soaking section temperature at 1219℃. The total furnace time is 10 min / cm, and the sum of the furnace time in the heating section and the soaking section accounts for 40% of the total furnace time. During rolling, a rough rolling process with full recrystallization is first adopted, with a rough rolling temperature of 1000℃ and a total reduction rate of 66.7%. Then, a finishing rolling process is carried out in the non-recrystallization zone, with an initial rolling temperature of 830℃ and a final rolling temperature of 780℃. During the finishing rolling process in the non-recrystallization zone, the thickness of the intermediate billet is 105mm. After rolling, ultra-rapid cooling is carried out from 790℃ at a cooling rate of 10℃ / s until it reaches 670℃. The billet is then stacked and cooled for 48 hours to finally obtain a 50mm thick steel plate with a low yield strength ratio and high strength for building structures. The steel plate is composed of the following components by weight percentage: C 0.185%, Si 0.30%, Mn 1.45%, P 0.015%, S 0.003%, Nb 0.025%, V 0.075%, N 0.0090%, balance being iron and its unavoidable impurities; The metallographic structure of the low yield strength ratio high strength building structure steel plate prepared in Example 10 is shown in the figure at 1 / 4 of the plate. Figure 1 As shown.

[0032] Example 11 The only difference between this embodiment and embodiment 10 is that in this embodiment, during the two-stage rolling of the non-recrystallized zone, the initial rolling temperature is 800℃, the final rolling temperature is 790℃, the intermediate billet thickness is 120mm during the two-stage rolling of the non-recrystallized zone, and after rolling, the ultra-fast cooling is accelerated to 668℃, finally obtaining a low yield strength ratio high strength building structure steel plate with a thickness of 55mm.

[0033] Example 12 The only difference between this embodiment and embodiment 10 is that in this embodiment, during the two-stage rolling of the non-recrystallized zone, the initial rolling temperature is 820°C, the final rolling temperature is 780°C, the intermediate billet thickness is 125mm during the two-stage rolling of the non-recrystallized zone, and after rolling, it is accelerated to 660°C by ultra-fast cooling, finally obtaining a 60mm thick steel plate for building structures with low yield strength ratio.

[0034] Comparative Example 1 The only difference between this comparative example and Example 1 is that, in this comparative example, during the two-stage rolling of the non-recrystallized zone, the initial rolling temperature is 1050°C, the final rolling temperature is 850°C, and the intermediate billet thickness is 25.4 mm. The steel plate is composed of the following components by weight percentage: C 0.17%, Si 0.26%, Mn 1.49%, P 0.014%, S 0.001%, Nb 0.036%, V 0.045%, CEV 0.44%, balance iron and its unavoidable impurities.

[0035] Comparative Example 2 The only difference between this comparative example and Example 5 is that, in this comparative example, during the two-stage rolling of the non-recrystallized zone in the finishing rolling process, the initial rolling temperature is 950°C, the final rolling temperature is 830°C, and the intermediate billet thickness is 38mm. The steel plate is composed of the following components by weight percentage: C 0.17%, Si 0.26%, Mn 1.49%, P 0.014%, S 0.001%, Nb 0.036%, V 0.045%, CEV 0.44%, balance iron and its unavoidable impurities.

[0036] Comparative Example 3 The only difference between this comparative example and Example 6 is that, in this comparative example, during the two-stage rolling of the non-recrystallized zone, the initial rolling temperature is 950°C, the final rolling temperature is 850°C, and the intermediate billet thickness is 56mm. The steel plate is composed of the following components by weight percentage: C 0.18%, Si 0.23%, Mn 1.50%, P 0.016%, S 0.001%, Nb 0.040%, V 0.043%, CEV 0.44%, balance iron and its unavoidable impurities.

[0037] Comparative Example 4 The only difference between this comparative example and Example 9 is that, in this comparative example, during the two-stage rolling of the non-recrystallized zone in the finishing rolling process, the initial rolling temperature is 900°C, the final rolling temperature is 850°C, and the intermediate billet thickness is 80mm. The steel plate is composed of the following components by weight percentage: C 0.18%, Si 0.23%, Mn 1.50%, P 0.016%, S 0.001%, Nb 0.040%, V 0.043%, CEV 0.44%, balance iron and its unavoidable impurities.

[0038] Comparative Example 5 The only difference between this comparative example and Example 10 is that, in this comparative example, during the two-stage rolling of the non-recrystallized zone, the initial rolling temperature is 880°C, the final rolling temperature is 835°C, and the intermediate billet thickness is 90 mm. The steel plate is composed of the following components by weight percentage: C 0.17%, Si 0.35%, Mn 1.53%, P 0.015%, S 0.002%, Nb 0.038%, V 0.047%, CEV 0.44%, balance iron and its unavoidable impurities.

[0039] Comparative Example 6 The only difference between this comparative example and Example 12 is that, in this comparative example, during the two-stage rolling of the non-recrystallized zone, the initial rolling temperature is 860°C, the final rolling temperature is 830°C, and the intermediate billet thickness is 100 mm. The steel plate is composed of the following components by weight percentage: C 0.17%, Si 0.35%, Mn 1.53%, P 0.015%, S 0.002%, Nb 0.038%, V 0.047%, CEV 0.44%, balance iron and its unavoidable impurities.

[0040] Experimental Example The structural steel plates prepared in Examples 1-12 and Comparative Examples 1-6 were subjected to the following performance tests: 1. The yield strength, tensile strength, and elongation were tested according to the test methods in GB / T 228.1-2021 "Metallic materials, tensile testing—Part 1: Tests at room temperature". The test results are shown in Table 1. 2. Longitudinal 0℃ Impact Energy Test: The Charpy impact energy of steel plate impact specimens for building structures was tested according to the method in GB / T 229-2020 "Metallic Materials Charpy Pendulum Impact Test Method". The test results are shown in Table 1. The test results are shown in Table 1: Table 1. Performance test results of steel plates used in building structures in Examples 1-12 and Comparative Examples 1-6

[0041] As can be seen from Table 1, the yield strength of the steel plates for building structures prepared in Examples 1-12 can reach 446-485 MPa, with an average of 463 MPa; the tensile strength can reach 610-655 MPa, with an average of 634 MPa; the elongation can reach 22.5%-27%, with an average of 24.8%; the yield strength ratio can reach 0.70-0.75, with an average of 0.73; and the longitudinal impact energy at 0℃ (equivalent to a 10mm×10mm×55mm sample) can reach 165-228 J, with an average of 188 J. This indicates that the steel plates for building structures prepared by the present invention have good mechanical properties and a low yield strength ratio, which is below 0.75, with an average of 0.73. This is 0.12 lower than the standard requirement of 0.85, and fully meets the safety and seismic resistance requirements of steel for building structures.

[0042] Compared with Comparative Examples 1-6, the yield strength ratio of the steel plates for building structures prepared in Examples 1, 5, 6, 9, 10, and 12 was significantly reduced. This indicates that in the preparation method of steel plates for building structures, by strictly controlling the rolling process, adopting a rolling method that combines rough rolling with full recrystallization and finish rolling with non-recrystallization, and reasonably adjusting the opening and closing rolling temperatures of the finish rolling without recrystallization suitable for different steel plate thicknesses, as well as reasonably adjusting the content of each component of the steel plate for building structures, the internal structure of steel plates of different thicknesses can be adjusted to obtain a uniform structure with high strength and high toughness, effectively reducing the yield strength ratio and achieving the target requirements.

[0043] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a steel plate with low yield strength ratio and high strength for building structures, characterized in that, This includes converter smelting, LF refining, RH vacuum degassing, continuous casting, slab stacking cooling, heating, and rolling; During the rolling process, rough rolling for complete recrystallization and finish rolling for the non-recrystallization zone are employed. When the thickness of the rolled steel plate is 8mm≤10mm≤, the thickness of the intermediate billet is ≥35mm, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 980~1000℃, and the final rolling temperature is ≤810℃. When 10mm < the thickness of the rolled steel plate ≤ 14mm, the thickness of the intermediate billet ≥ 40mm, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 930~950℃, and the final rolling temperature is ≤ 810℃. When 14mm < the thickness of the rolled steel plate ≤ 16mm, the thickness of the intermediate billet ≥ 55mm, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 910~930℃, and the final rolling temperature is ≤ 810℃. When 16mm < the thickness of the rolled steel plate ≤ 30mm, the thickness of the intermediate billet ≥ 3t, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 860~880℃, and the final rolling temperature is ≤ 800℃. When 30mm < rolled steel plate thickness ≤ 40mm, the intermediate billet thickness ≥ 2.5t, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 830~850℃, and the final rolling temperature is ≤ 790℃. When 40mm < the thickness of the rolled steel plate ≤ 50mm, the thickness of the intermediate billet ≥ 2t, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 810~830℃, and the final rolling temperature is ≤ 790℃. When 50mm < the thickness of the rolled steel plate ≤ 60mm, the thickness of the intermediate billet ≥ 120mm, the initial rolling temperature during finishing rolling in the non-recrystallization zone is 800~820℃, and the final rolling temperature is ≤ 790℃.

2. The method for preparing a low yield strength ratio high strength building structure steel plate according to claim 1, characterized in that, The steel plate is composed of the following components by weight percentage: C 0.16%~0.19%, Si 0.20%~0.45%, Mn 1.40%~1.50%, P≤0.018%, S≤0.005%, Nb 0.020%~0.030%, V 0.065%~0.080%, N 0.0090%~0.014%, with the balance being iron and its unavoidable impurities.

3. The method for preparing a low yield strength ratio high strength building structure steel plate according to claim 1, characterized in that, During the roughing and fully recrystallized rolling process, the temperature is 1000~1100℃ and the total reduction rate is >60%.

4. The method for preparing a low yield strength ratio high strength building structure steel plate according to claim 1, characterized in that, The heating process employs either dual-furnace heating or triple-furnace heating.

5. The method for preparing a low yield strength ratio high strength building structure steel plate according to claim 1, characterized in that, During the heating process, the temperature of the heating section is 1180~1260℃, the temperature of the soaking section is 1210~1250℃, the total furnace time is 10~13 min / cm, and the sum of the furnace time of the heating section and the soaking section is 40%~50% of the total furnace time.

6. The method for preparing a low yield strength ratio high strength building structure steel plate according to claim 1, characterized in that, During the RH vacuum degassing process, the bottom blowing of the RH furnace is switched from argon to nitrogen, and nitrogen is blown throughout the process to increase N, controlling the nitrogen content to be 0.0090%~0.014%.

7. The method for preparing a low yield strength ratio high strength building structure steel plate according to claim 1, characterized in that, During continuous casting, the superheat is 15~25℃.

8. The method for preparing a low yield strength ratio high strength building structure steel plate according to claim 1, characterized in that, When the thickness of the rolled steel plate is 16mm or less and 60mm or less, the rolling process includes ultra-rapid cooling, with an initial cooling temperature of 740~790℃ and a cooling rate of 6~10℃ / s.

9. The method for preparing a low yield strength ratio high strength building structure steel plate according to claim 8, characterized in that, When the thickness of the rolled steel plate is 40mm or less and 60mm or less, the ultra-rapid cooling also includes the stacking cooling of the steel plate.

10. The method for preparing a low yield strength ratio high strength building structure steel plate according to claim 9, characterized in that, When the steel plate is stacked and cooled, the cooling temperature is 350~550℃ and the cooling time is 48h.

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