A method for producing ultra-high strength steel plates with a yield strength of 1000 MPa

Abstract

This invention discloses a method for producing ultra-high strength steel plates with a yield strength of 1000 MPa, comprising: (1) smelting; (2) continuous casting; (3) heating and rolling; and (4) heat treatment. The chemical composition of the steel plate, by weight percentage, is C: 0.130-0.139%, Si: 0.30-0.35%, Mn: 0.90-0.99%, P: ≤0.015%, S: ≤0.010%, Cr: 0.41-0.51%, Als: 0.024-0.038%, Ti: 0.014-0.016%, B: 0.0010-0.0015%, Ce: 0.0011-0.0013%, with the balance being Fe and unavoidable impurities. The purpose of this invention is to obtain ultra-high strength steel plates with high bending performance through rare earth alloy composition design combined with corresponding rolling and heat treatment processes.

Description

Technical Field

[0001] This invention belongs to the field of high-strength steel technology, and in particular relates to a method for producing ultra-high-strength steel plates with a yield strength of 1000MPa. Background Technology

[0002] Currently, my country has become a major manufacturer of construction machinery, ranking first globally in both production and sales. High-strength steel is a key raw material for construction machinery. In recent years, with the rapid development of the national economy, resource and energy constraints have become increasingly prominent, and environmental issues have become more severe. The construction machinery industry is developing towards larger, lighter, and heavier load-bearing structures, requiring lighter structural components with stronger load-bearing capacity, which places higher demands on the steel used in construction machinery. To achieve lightweight construction equipment while improving its load-bearing capacity, more and higher-grade structural steel plates are needed, making the upgrading of raw materials extremely urgent. The development of structural steel for construction machinery towards high strength, high toughness, easy formability, and weldability has become an inevitable trend.

[0003] The invention disclosed in application publication number CN120099426A is a hot-rolled tempered steel plate with a low yield strength ratio of over 1100MPa and a production method thereof. The steel plate composition is C: 0.14%~0.17%, Si: 0.15%~0.25%, Mn: 1.15%~1.25%, P≤0.015%, S≤0.003%, Al: 0.001%~0.01%, Mo: 0.45%~0.55%, Cr: 0.3%~0.4%, Ni: 0.3%~0.5%, with the remainder being Fe and impurities. This invention employs a composition design that incorporates Cr, Mo, and Ni into low-carbon steel. Hot-rolled steel plates are produced through smelting, continuous casting, rolling, and tempering. The finished steel plates exhibit a yield strength ≥1100 MPa, tensile strength of 1120–1300 MPa, hardness ≥350 HBW, elongation ≥8%, and a microstructure of tempered martensite + bainite. A continuous heat treatment and cross-cutting process is used for rapid and efficient production of steel plates with a thickness ≤6 mm, a maximum width of 1500 mm, and high low-temperature impact toughness, a low yield strength ratio, and high wear resistance. The difference between this invention and the aforementioned inventions lies primarily in their significantly different composition design. This invention's composition design does not contain precious metals such as Ni and Mo, resulting in lower alloy costs and a clear cost advantage. The manufacturing process of this invention also differs significantly from the aforementioned inventions. Furthermore, the thickness of the steel plates produced by this invention is also significantly different from that of the aforementioned inventions.

[0004] The invention disclosed in publication number CN111500935B is a 1000MPa grade high-strength steel, its preparation method, and its applications. The high-strength steel is composed of the following chemical components by mass fraction: C: 0.06–0.18%; Si: 0.20–0.30%; Mn: 1.2–2.0%; P≤0.010%; S≤0.003%; Al: 0.02–0.04%; Ti: 0.06%–0.12%; the remainder being Fe and unavoidable impurities. Using this invention, high-strength steel with a thickness of 0.6–1.5 mm can be produced, with a yield strength exceeding 1000 MPa and a tensile strength exceeding 1100 MPa. It also possesses excellent plate shape and surface quality, meeting the requirement of not cracking when bent at 90°. Furthermore, it boasts high production efficiency, fewer alloys, and low cost. The difference between this invention and the aforementioned invention lies primarily in the significantly different composition design. The manufacturing process of this invention also differs significantly from the aforementioned invention. The thickness of the steel plate produced by this invention is also significantly different from that of the inventions described above.

[0005] The invention disclosed in application publication number CN117418166A is a 1000MPa grade hot-rolled high-strength steel and its preparation method. The technical problem to be solved is to provide a 1000MPa grade hot-rolled high-strength steel and its preparation method. The chemical composition of the steel, by weight percentage, includes: C: 0.07-0.15%, Si: 0.05-0.20%, Mn: 1.5-2.5%, V+Ti+Zr: 0.20-0.35%, Als: 0.010-0.060%, P≤0.015%, S≤0.005%, N≤0.0050%, with the balance being Fe and unavoidable impurities. The microstructure of the hot-rolled high-strength steel of this invention is ferrite, with a yield strength ≥900MPa, tensile strength ≥1000MPa, elongation ≥12%, passable 180° cold bending d=2a, expansion rate ≥25%, and impact energy at 0℃ ≥45J. The difference between this invention and the aforementioned inventions lies primarily in their composition design; this invention's composition does not contain precious metals such as V and Zr. The manufacturing process of this invention also differs significantly from the aforementioned inventions. Furthermore, the thickness of the steel plate produced by this invention is also significantly different from that of the aforementioned inventions. Summary of the Invention

[0006] To obtain ultra-high strength steel plates with a yield strength of 1000MPa and a thickness of 10~20mm, the purpose of this invention is to provide a production method for ultra-high strength steel plates with a yield strength of 1000MPa. By designing rare earth alloy composition and combining it with corresponding rolling and heat treatment processes, ultra-high strength steel plates with high bending performance can be obtained.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] This invention discloses a method for producing ultra-high strength steel plates with a yield strength of 1000 MPa, comprising:

[0009] (1) Smelting

[0010] According to the composition design of this invention, molten steel is smelted through a blast furnace, converter, refining furnace, and RH furnace to obtain molten steel with qualified composition; wherein the vacuum holding time in the RH furnace smelting process is greater than 15 minutes, the nitrogen content in the molten steel is less than 40 ppm, and the hydrogen content is less than 2.0 ppm.

[0011] (2) Continuous casting

[0012] Molten steel with qualified composition is continuously cast to obtain a continuously cast slab with a thickness of 150~300mm. After the continuously cast slab is cut, it is slowly cooled.

[0013] (3) Heating and rolling

[0014] The slab is heated, rough rolled, and finish rolled to obtain the base plate; the furnace exit temperature of the continuously cast slab is selected at 1190~1220℃; the steel plate adopts two-stage rolling, the finishing rolling temperature is selected at 810~830℃, and after rolling, it is water cooled to 650~680℃, and then slowly cooled to room temperature.

[0015] (4) Heat treatment

[0016] The steel plate obtained above is subjected to quenching and tempering heat treatment; the quenching heating and holding temperature is 890±10℃, and the quenching holding time is 22-40min. After the holding time is completed, the steel plate is taken out of the furnace and quenched by a quenching machine. The temperature of the steel plate after quenching is ≤50℃; the tempering heating and holding temperature is 270±10℃, and the steel plate is held for 20-30min. After the holding time is completed, the steel plate is taken out of the furnace and cooled slowly; thus, the steel plate of the present invention is obtained.

[0017] The chemical composition of the steel plate, by weight percentage, is C: 0.130-0.139%, Si: 0.30-0.35%, Mn: 0.90-0.99%, P: ≤0.015%, S: ≤0.010%, Cr: 0.41-0.51%, Als: 0.024-0.038%, Ti: 0.014-0.016%, B: 0.0010-0.0015%, Ce: 0.0011-0.0013%, with the balance being Fe and unavoidable impurities.

[0018] Furthermore, the chemical composition of the steel plate by weight percentage is C: 0.130%, Si: 0.35%, Mn: 0.90%, P: 0.012%, S: 0.003%, Cr: 0.41%, Als: 0.024%, Ti: 0.014%, B: 0.0010%, Ce: 0.0012%, with the balance being Fe and unavoidable impurities.

[0019] Furthermore, the chemical composition of the steel plate by weight percentage is C: 0.134%, Si: 0.31%, Mn: 0.97%, P: 0.011%, S: 0.003%, Cr: 0.47%, Als: 0.032%, Ti: 0.015%, B: 0.0012%, Ce: 0.0011%, with the balance being Fe and unavoidable impurities.

[0020] Furthermore, the chemical composition of the steel plate by weight percentage is C: 0.139%, Si: 0.30%, Mn: 0.99%, P: 0.012%, S: 0.003%, Cr: 0.51%, Als: 0.038%, Ti: 0.016%, B: 0.0015%, Ce: 0.0013%, with the balance being Fe and unavoidable impurities.

[0021] Furthermore, specifically, this includes: the furnace exit temperature for continuous casting slab rolling is 1220℃, the slab is rolled, the finishing rolling temperature of the slab is 830℃, and it is then water-cooled to 680℃. The quenching holding temperature is 880℃, held for 25 minutes, followed by quenching. The tempering holding temperature is 260℃, held for 20 minutes, and then the slab is slowly cooled after being removed from the furnace.

[0022] Furthermore, specifically, this includes: the furnace exit temperature for continuous casting slab rolling is 1200℃, the slab is rolled, the finishing rolling temperature of the slab is 820℃, and it is then water-cooled to 660℃. The quenching holding temperature is 890℃, held for 30 minutes, followed by quenching. The tempering holding temperature is 270℃, held for 25 minutes, and then the slab is slowly cooled after being removed from the furnace.

[0023] Furthermore, specifically, this includes: the furnace exit temperature for continuous casting slab rolling is 1190℃, the slab is rolled, the finishing rolling temperature of the slab is 810℃, and it is then water-cooled to 650℃. The quenching holding temperature is 900℃, held for 40 minutes, followed by quenching. The tempering holding temperature is 280℃, held for 30 minutes, and then the slab is slowly cooled after being removed from the furnace.

[0024] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0025] This invention provides an ultra-high strength steel plate with a yield strength of 1000MPa and a thickness of 10~20mm. Through the design of rare earth alloy composition and the combination of corresponding rolling and heat treatment processes, this invention can obtain an ultra-high strength steel plate with ultra-high strength and high bending performance. Detailed Implementation

[0026] The present invention aims to provide an ultra-high strength steel plate with a yield strength of 1000MPa and a thickness of 10~20mm. The present invention obtains an ultra-high strength steel plate with ultra-high strength and high bending performance by designing rare earth alloy composition and combining it with corresponding rolling and heat treatment processes.

[0027] The production method includes the following steps:

[0028] 1. Smelting

[0029] According to the composition design of this invention, molten steel is smelted through a blast furnace, converter, refining furnace, and RH furnace to obtain molten steel with qualified composition. The vacuum holding time in the RH furnace smelting process must be greater than 15 minutes, and the nitrogen content in the molten steel must be less than 40 ppm and the hydrogen content less than 2.0 ppm.

[0030] 2. Continuous casting

[0031] Molten steel with qualified composition is continuously cast to obtain a continuously cast slab with a thickness of 150~300mm. After the continuously cast slab is cut, it is slowly cooled.

[0032] 3. Heating and rolling

[0033] The slab is heated, rough-rolled, and finish-rolled to obtain a hot-rolled substrate. The furnace exit temperature of the continuously cast slab during heating is selected to be 1190~1220℃. The steel plate adopts a two-stage rolling process, with the finishing rolling temperature selected to be 810~830℃, followed by water cooling to 650~680℃, and then slow cooling to room temperature.

[0034] 4. Heat treatment

[0035] The steel plate obtained above is subjected to quenching and tempering heat treatment. The quenching temperature is 890±10℃, and the holding time is 22–40 min. After holding, the steel plate is removed from the furnace and quenched using a quenching machine until the temperature of the steel plate is ≤50℃. The tempering temperature is 270±10℃, and the holding time is 20–30 min. After tempering, the steel plate is removed from the furnace and slowly cooled. This yields the steel plate product described in this invention.

[0036] Example 1

[0037] The chemical composition of Example 1 is shown in Table 1. The furnace exit temperature for continuous casting slab rolling was 1220℃. The slab was rolled at a finishing rolling temperature of 830℃, followed by water cooling to 680℃. The quenching holding temperature was 880℃ for 25 minutes, followed by quenching. The tempering holding temperature was 260℃ for 20 minutes, followed by slow cooling after removal from the furnace. The mechanical properties of the steel plate are shown in Table 2.

[0038] Example 2

[0039] The chemical composition of Example 2 is shown in Table 1. The furnace exit temperature for continuously cast slab rolling was 1200℃. The slab was rolled at a finishing rolling temperature of 820℃, followed by water cooling to 660℃. The quenching holding temperature was 890℃ for 30 minutes, followed by quenching. The tempering holding temperature was 270℃ for 25 minutes, followed by slow cooling after removal from the furnace. The mechanical properties of the steel plate are shown in Table 2.

[0040] Example 3

[0041] The chemical composition of Example 3 is shown in Table 1. The furnace exit temperature for continuous casting slab rolling was 1190℃. The slab was rolled at a finishing rolling temperature of 810℃, followed by water cooling to 650℃. The quenching holding temperature was 900℃ for 40 minutes, followed by quenching. The tempering holding temperature was 280℃ for 30 minutes, followed by slow cooling after removal from the furnace. The mechanical properties of the steel plate are shown in Table 2.

[0042] Table 1: Chemical composition (wt%) of steel plates from the examples

[0043] Serial Number Thickness (mm) C Si Mn P S Cr Ti B Als Ce Example 1 10 0.13 0.35 0.9 0.012 0.003 0.41 0.014 0.001 0.024 0.0012 Example 2 15 0.134 0.31 0.97 0.011 0.003 0.47 0.015 0.0012 0.032 0.0011 Example 3 20 0.139 0.3 0.99 0.012 0.003 0.51 0.016 0.0015 0.038 0.0013

[0044] Table 2: Steel Plate Properties of Examples

[0045] Serial Number Specifications / mm Yield strength / MPa Tensile strength / MPa <![CDATA[Elongation A 50 / %]]> <![CDATA[-20°C impact KV2 / J]]> Bending D=3a, 90°, b=20mm Example 1 10 1033 1137 21.5 92 qualified Example 2 15 1022 1119 20.5 88 qualified Example 3 20 1024 1125 20.0 77 qualified

[0046] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for producing ultra-high strength steel plates with a yield strength of 1000 MPa, characterized in that: include: (1) Smelting According to the composition design of this invention, molten steel is smelted through a blast furnace, converter, refining furnace, and RH furnace to obtain molten steel with qualified composition. The vacuum holding time in the RH furnace smelting process must be greater than 15 minutes, the nitrogen content in the molten steel must be less than 40 ppm, and the hydrogen content must be less than 2.0 ppm. (2) Continuous casting Molten steel with qualified composition is continuously cast to obtain a continuously cast slab with a thickness of 150~300mm. After the continuously cast slab is cut, it is slowly cooled. (3) Heating and rolling The slab is heated, rough rolled, and finish rolled to obtain the base plate; the furnace exit temperature of the continuously cast slab is selected at 1190~1220℃; the steel plate adopts two-stage rolling, the finishing rolling temperature is selected at 810~830℃, and after rolling, it is water cooled to 650~680℃, and then slowly cooled to room temperature. (4) Heat treatment The steel plate obtained above is subjected to quenching and tempering heat treatment; the quenching heating and holding temperature is 890±10℃, and the quenching holding time is 22-40min. After the holding time is completed, the steel plate is taken out of the furnace and quenched by a quenching machine. The temperature of the steel plate after quenching is ≤50℃; the tempering heating and holding temperature is 270±10℃, and the steel plate is held for 20-30min. After the holding time is completed, the steel plate is taken out of the furnace and cooled slowly; thus, the steel plate of the present invention is obtained. The chemical composition of the steel plate, by weight percentage, is C: 0.130-0.139%, Si: 0.30-0.35%, Mn: 0.90-0.99%, P: ≤0.015%, S: ≤0.010%, Cr: 0.41-0.51%, Als: 0.024-0.038%, Ti: 0.014-0.016%, B: 0.0010-0.0015%, Ce: 0.0011-0.0013%, with the balance being Fe and unavoidable impurities.

2. The method for producing ultra-high strength steel plates with a yield strength of 1000 MPa according to claim 1, characterized in that: The chemical composition of the steel plate by weight percentage is C: 0.130%, Si: 0.35%, Mn: 0.90%, P: 0.012%, S: 0.003%, Cr: 0.41%, Als: 0.024%, Ti: 0.014%, B: 0.0010%, Ce: 0.0012%, with the balance being Fe and unavoidable impurities.

3. The method for producing ultra-high strength steel plates with a yield strength of 1000 MPa according to claim 1, characterized in that: The chemical composition of the steel plate by weight percentage is C: 0.134%, Si: 0.31%, Mn: 0.97%, P: 0.011%, S: 0.003%, Cr: 0.47%, Als: 0.032%, Ti: 0.015%, B: 0.0012%, Ce: 0.0011%, with the balance being Fe and unavoidable impurities.

4. The method for producing ultra-high strength steel plates with a yield strength of 1000 MPa according to claim 1, characterized in that: The chemical composition of the steel plate by weight percentage is C: 0.139%, Si: 0.30%, Mn: 0.99%, P: 0.012%, S: 0.003%, Cr: 0.51%, Als: 0.038%, Ti: 0.016%, B: 0.0015%, Ce: 0.0013%, with the balance being Fe and unavoidable impurities.

5. The method for producing ultra-high strength steel plates with a yield strength of 1000 MPa according to claim 2, characterized in that: Specifically, it includes: The furnace exit temperature for continuous casting slab rolling is 1220℃. The slab is rolled to a finishing rolling temperature of 830℃, followed by water cooling to 680℃. The quenching holding temperature is 880℃ for 25 minutes, followed by quenching. The tempering holding temperature is 260℃ for 20 minutes, after which the slab is removed from the furnace and allowed to cool slowly.

6. The method for producing ultra-high strength steel plates with a yield strength of 1000 MPa according to claim 3, characterized in that: Specifically, it includes: The furnace exit temperature for continuous casting slab rolling is 1200℃. The slab is rolled to a finishing rolling temperature of 820℃, followed by water cooling to 660℃. The quenching holding temperature is 890℃ for 30 minutes, followed by quenching. The tempering holding temperature is 270℃ for 25 minutes, after which the slab is removed from the furnace and slowly cooled.

7. The method for producing ultra-high strength steel plates with a yield strength of 1000 MPa according to claim 4, characterized in that: Specifically, it includes: The furnace exit temperature for continuous casting slab rolling is 1190℃. The slab is rolled to a finishing rolling temperature of 810℃, followed by water cooling to 650℃. The quenching holding temperature is 900℃ for 40 minutes, followed by quenching. The tempering holding temperature is 280℃ for 30 minutes, after which the slab is removed from the furnace and slowly cooled.