A thick Q500qF bridge plate and its manufacturing method

Abstract

This invention discloses a thick Q500qF bridge plate and its production method, belonging to the field of metallurgical technology. The chemical composition of the bridge plate, by mass percentage, is as follows: C: 0.07-0.11%, Mn: 1.70-2.00%, Cr: 0.35-0.70%, P≤0.015%, S≤0.005%, Nb: 0.015-0.045%, Mo: 0.15-0.45%, with the remainder being Fe and unavoidable impurities. The sum of the above components is 100%. The production method includes converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment. This method adopts a low C content composition design, and by adding Nb, Cr, and Mo in combination, and through a special rolling controlled cooling mode, a bainitic + ferrite + martensite multiphase steel plate is obtained, ensuring that the strength, extremely low yield strength ratio, -60℃ low temperature impact, impact fiber ratio, and aging impact meet the requirements.

Description

Technical Field

[0001] This invention relates to a bridge plate and its manufacturing method, specifically to a thick Q500qF bridge plate and its manufacturing method, belonging to the field of metallurgical technology. Background Technology

[0002] With the increasing application of high-strength bridge steel in key national projects, especially with the increasing investment in construction in the western regions of the country, which are remote areas with high altitudes and complex terrain, the steel used in the assembly and design projects is complex and has high performance requirements. Large-thickness steel plates are needed to reduce the amount of welding in the butt welds and reduce the difficulty of construction.

[0003] Meanwhile, the complex environment in such areas necessitates careful consideration of bridge construction safety during the design phase. This requires the development of cold-resistant bridge decks with wide widths and high performance to improve the fracture toughness, low-temperature toughness, and seismic resistance of the steel.

[0004] Patent application CN112210719A discloses a low-cost, high-performance Q500 bridge steel and its production method: the steel plate composition system requires the addition of V and Cu, and the thickness is 10-60mm. The thickness range of the produced steel plates is small and cannot meet the needs of remote areas with high altitude and complex terrain.

[0005] Patent CN 114381663 A discloses a 100mm thick HPS420WZ35 weathering bridge plate and its production method to ensure performance. The steel plate has a strength of 420MPa, which is low, and the thickness is only 100mm; this patent does not cover thicknesses greater than 100mm. Patent CN 114262845 B discloses a 500MPa grade thin-gauge bridge plate and its production method. This patent relates to a method for producing bridge plates with a strength level of 500MPa or higher, delivered in a tempering-free TMCP state, and with specifications ranging from 6 to 16m. However, the produced steel plate has a small thickness range, which cannot meet the needs of remote areas with high altitudes and complex terrain.

[0006] Therefore, developing a thick Q500qF bridge plate that can overcome the above defects and its production method has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] The technical problem to be solved by this invention is to address the shortcomings of the existing technology by proposing a thick Q500qF bridge plate and its production method. This method adopts a low C content composition design and adds Nb, Cr and Mo in a composite manner. Through a special rolling controlled cooling mode, a multiphase steel plate with bainitic + ferrite + martensite structure is obtained, ensuring that the strength, extremely low yield strength ratio, -60℃ low temperature impact, impact fiber ratio and aging impact meet the requirements.

[0008] The technical solution of this invention to solve the above technical problems is:

[0009] A thick Q500qF bridge deck, the chemical composition of which, by mass percentage, is as follows: C: 0.07-0.11%, Mn: 1.70-2.00%, Cr: 0.35-0.70%, P≤0.015%, S≤0.005%, Nb: 0.015-0.045%, Mo: 0.15-0.45%, with the remainder being Fe and unavoidable impurities, the sum of the above components being 100%.

[0010] Technical benefits: This invention employs low-carbon C (0.07-0.11%) and a multiphase microstructure design to improve the seismic safety factor.

[0011] This invention also designs a method for producing thick Q500qF bridge plates. The production process includes converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein:

[0012] (1) Rolling process: In order to obtain multiphase structure and improve the toughness of steel plate, the rough rolling temperature is 900-980℃, the finishing rolling temperature is 700-750℃, and the water immersion temperature is 500-630℃.

[0013] (2) Controlled cooling process in rolling: The temperature of the steel plate when it turns red is limited to 400-500℃;

[0014] (3) Heat treatment process: Tempering is carried out at a temperature of 480-600℃ to eliminate surface stress of steel plate and improve mechanical properties.

[0015] The technical solution further defined in this invention is as follows:

[0016] In the aforementioned production method of thick Q500qF bridge plates, the steel plate is refined using LF+RH refining to ensure that the gas H content of the steel plate is ≤0.5ppm and the N content is ≤35ppm.

[0017] In the aforementioned production method of thick Q500qF bridge plates, the thickness of the produced bridge plates is 100-150mm.

[0018] Technical advantages: The bridge plates produced by this invention have a thickness of 100-150mm, which is much higher than the design thickness of ordinary bridge plates. This makes them more suitable for remote areas with high altitudes and complex terrain. The thick steel plates reduce the amount of welding required for butt welds and lower the difficulty of construction.

[0019] In the aforementioned production method of thick Q500qF bridge deck, the produced bridge deck has a yield strength ≥500Mpa, tensile strength 630-750Mpa, elongation ≥18%, conventional impact strength at -60℃ ≥250J, and yield strength ratio ≤0.86.

[0020] In the aforementioned production method of thick Q500qF bridge deck, the produced bridge deck has an impact cross-sectional fiber content of ≥90% and an aging impact performance of ≥150J with 5% deformation.

[0021] Technical benefits include excellent performance with a yield strength ≥500 MPa, tensile strength 630-750 MPa, elongation ≥18%, conventional impact strength at -60℃ ≥250 J, yield-to-tensile ratio ≤0.86, fiber content in impact section ≥90%, and aging impact performance with 5% deformation ≥150 J. These indicators can significantly improve the welding and assembly characteristics of steel plates to adapt to the high altitude and complex laying environment in western regions.

[0022] The beneficial effects of this invention are:

[0023] (1) Low-temperature austenitization technology reduces the original austenite grain size, ensuring the stability of the product's low-temperature impact toughness; (2) By controlling the second-stage rolling temperature, final rolling temperature, and relaxation technology, combined with water cooling process, the yield strength of the product is effectively reduced, ensuring the stability of tensile strength and the stability of the product's yield strength ratio; (3) By controlling the controlled cooling process, the grain size of the microstructure is effectively refined, and the microstructure transformation is ensured by the second-stage rolling temperature and water immersion temperature, obtaining a multiphase microstructure with polygonal ferrite, bainite, martensite, etc., thereby improving the strength and toughness of the steel plate. Compared with the Q500qF steel plate produced by ordinary quenching and tempering, it has a high yield strength ratio, poor weldability, and small excess impact toughness.

[0024] The production method of this invention adopts a low C content composition design, and by adding Nb, Cr and Mo composite, and through a special rolling controlled cooling mode, a multiphase steel plate with bainite + ferrite + martensite structure is obtained, which ensures that the strength, extremely low yield strength ratio, -60℃ low temperature impact, impact fiber ratio and aging impact meet the requirements.

[0025] In the controlled rolling process of this invention, the roughing temperature is 900-980℃, the finishing temperature is 700-750℃, and the water immersion temperature is 500-630℃. This is to control the rolling of the continuously cast billet in the austenite recrystallization zone, the non-recrystallization zone, and the deformation-induced phase transformation zone, so that a large number of dislocations are formed inside the steel plate and a large distortion energy is retained, achieving the purpose of repeatedly refining austenite grains. This results in the generation of fine ferrite and bainite grains in the subsequent controlled cooling process, thereby ensuring the low yield strength ratio and low-temperature impact toughness of the steel plate. Simultaneously, by controlling the water immersion temperature and using relaxation technology, the ferrite content is increased, further effectively reducing the yield strength ratio. The controlled cooling process of this invention uses rapid ACC cooling with a red-hot temperature of 400-500℃, ensuring that the bainitic phase transformation is completed throughout the thickness direction, improving the high strength and toughness of the steel plate. At the same time, the higher red-hot temperature can prevent secondary warping of the steel plate due to uneven cooling, ensuring a straight plate shape and reducing the generation of corrugations.

[0026] The heat treatment of this invention uses tempering at a temperature of 480-600℃ to eliminate surface stress on the steel plate and improve its mechanical properties. Detailed Implementation

[0027] To make the present invention clearer, the following further describes a thick Q500qF bridge plate and its production method. The specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Example 1

[0028] This embodiment provides a thick Q500qF bridge plate with a thickness of 100mm. Its chemical composition and mass percentage are shown in Table 1. The remainder is Fe and unavoidable impurities. The sum of the above components is 100%.

[0029] The production method for the aforementioned Q500qF bridge plate includes a production process comprising converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein:

[0030] (1) During refining, the steel plate is refined using LF+RH, so that the gas H content of the steel plate is 0.5ppm and the N content is 35ppm;

[0031] (2) Rolling process: roughing temperature 900℃, finishing temperature 700℃, water immersion temperature 630℃;

[0032] (3) Controlled cooling process in rolling: The temperature of the steel plate when it turns red is limited to 400℃;

[0033] (4) Heat treatment process: Tempering is carried out at 480℃ to eliminate surface stress of the steel plate.

[0034] The mechanical properties of the thick Q500qF bridge plate obtained in this implementation are shown in Table 2. Example 2

[0035] This embodiment provides a thick Q500qF bridge plate with a thickness of 110mm. Its chemical composition and mass percentage are shown in Table 1. The remainder is Fe and unavoidable impurities. The sum of the above components is 100%.

[0036] The production method for the aforementioned Q500qF bridge plate includes a production process comprising converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein:

[0037] (1) During refining, the steel plate is refined using LF+RH, resulting in a gas H content of 0.4ppm and a N content of 32ppm.

[0038] (2) Rolling process: roughing temperature 970℃, finishing temperature 710℃, water immersion temperature 600℃;

[0039] (3) Controlled cooling process in rolling: The temperature of the steel plate when it turns red is limited to 420℃;

[0040] (4) Heat treatment process: Tempering is carried out at 490℃ to eliminate surface stress of steel plate.

[0041] The mechanical properties of the thick Q500qF bridge plate obtained in this implementation are shown in Table 2. Example 3

[0042] This embodiment provides a thick Q500qF bridge plate with a thickness of 125mm. Its chemical composition and mass percentage are shown in Table 1. The remainder is Fe and unavoidable impurities. The sum of the above components is 100%.

[0043] The production method for the aforementioned Q500qF bridge plate includes a production process comprising converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein:

[0044] (1) During refining, the steel plate is refined using LF+RH, resulting in a gas H content of 0.42ppm and a N content of 31ppm.

[0045] (2) Rolling process: roughing temperature 960℃, finishing temperature 720℃, water immersion temperature 610℃;

[0046] (3) Controlled cooling process in rolling: The reddening temperature of the steel plate is limited to 435℃;

[0047] (4) Heat treatment process: Tempering is carried out at 520℃ to eliminate surface stress of steel plate.

[0048] The mechanical properties of the thick Q500qF bridge plate obtained in this implementation are shown in Table 2. Example 4

[0049] This embodiment provides a thick Q500qF bridge plate with a thickness of 130mm. Its chemical composition and mass percentage are shown in Table 1. The remainder is Fe and unavoidable impurities. The sum of the above components is 100%.

[0050] The production method for the aforementioned Q500qF bridge plate includes a production process comprising converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein:

[0051] (1) During refining, the steel plate is refined using LF+RH, so that the gas H content of the steel plate is 0.35ppm and the N content is 30ppm;

[0052] (2) Rolling process: roughing temperature 930℃, finishing temperature 720℃, water immersion temperature 600℃;

[0053] (3) Controlled cooling process in rolling: The temperature of the steel plate when it turns red is limited to 470℃;

[0054] (4) Heat treatment process: Tempering is carried out at 540℃ to eliminate surface stress of the steel plate.

[0055] The mechanical properties of the thick Q500qF bridge plate obtained in this implementation are shown in Table 2. Example 5

[0056] This embodiment provides a thick Q500qF bridge plate with a thickness of 140mm. Its chemical composition and mass percentage are shown in Table 1. The remainder is Fe and unavoidable impurities. The sum of the above components is 100%.

[0057] The production method for the aforementioned Q500qF bridge plate includes a production process comprising converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein:

[0058] (1) During refining, the steel plate is refined using LF+RH, resulting in a gas H content of 0.38ppm and a N content of 30ppm.

[0059] (2) Rolling process: roughing temperature 920℃, finishing temperature 700℃, water immersion temperature 540℃;

[0060] (3) Controlled cooling process in rolling: The temperature of the steel plate when it turns red is limited to 480℃;

[0061] (4) Heat treatment process: Tempering is carried out at 580℃ to eliminate surface stress of the steel plate.

[0062] The mechanical properties of the thick Q500qF bridge plate obtained in this implementation are shown in Table 2. Example 6

[0063] This embodiment provides a thick Q500qF bridge plate with a thickness of 145mm. Its chemical composition and mass percentage are shown in Table 1. The remainder is Fe and unavoidable impurities. The sum of the above components is 100%.

[0064] The production method for the aforementioned Q500qF bridge plate includes a production process comprising converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein:

[0065] (1) During refining, the steel plate is refined using LF+RH, resulting in a gas H content of 0.45ppm and a N content of 25ppm.

[0066] (2) Rolling process: roughing temperature 910℃, finishing temperature 710℃, water immersion temperature 510℃;

[0067] (3) Controlled cooling process in rolling: The temperature of the steel plate when it turns red is limited to 480℃;

[0068] (4) Heat treatment process: Tempering is carried out at a temperature of 590℃ to eliminate surface stress of the steel plate.

[0069] The mechanical properties of the thick Q500qF bridge plate obtained in this implementation are shown in Table 2. Example 7

[0070] This embodiment provides a thick Q500qF bridge plate with a thickness of 150mm. Its chemical composition and mass percentage are shown in Table 1. The remainder is Fe and unavoidable impurities. The sum of the above components is 100%.

[0071] The production method for the aforementioned Q500qF bridge plate includes a production process comprising converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein:

[0072] (1) During refining, the steel plate is refined using LF+RH, resulting in a gas H content of 0.36ppm and a N content of 30ppm.

[0073] (2) Rolling process: roughing temperature 900℃, finishing temperature 700℃, water immersion temperature 500℃;

[0074] (3) Controlled cooling process in rolling: The temperature of the steel plate when it turns red is limited to 490℃;

[0075] (4) Heat treatment process: Tempering is carried out at 600℃ to eliminate surface stress of steel plate.

[0076] The mechanical properties of the thick Q500qF bridge plate obtained in this implementation are shown in Table 2.

[0077] Table 1. Chemical composition of bridge plates in Examples 1-7

[0078] Example sequence number C（%） Mn (%) P（%） S（%） Cr（%） Nb (%) Mo (%) 1 0.07 1.70 0.012 0.003 0.35 0.015 0.15 2 0.08 1.75 0.010 0.002 0.42 0.035 0.25 3 0.08 1.83 0.008 0.003 0.51 0.040 0.28 4 0.07 1.91 0.008 0.002 0.57 0.041 0.35 5 0.09 1.95 0.006 0.002 0.65 0.039 0.40 6 0.11 1.97 0.010 0.002 0.68 0.042 0.41 7 0.10 2.00 0.010 0.003 0.70 0.045 0.45

[0079] Table 2. Mechanical performance data of bridge decks in Examples 1-7

[0080] Example sequence number Yield strength MPa Tensile strength MPa elongation % The ratio of yield strength Impact energy at -60℃ (J) -60℃ impact section fiber content % Impact energy at -60℃ (5% deformation) J 1 512 677 21 0.76 275，289，295 95，100，100 170，200，212 2 522 685 22 0.76 300，310，299 100，100，100 199，201，220 3 531 690 22 0.77 282，301，288 100，100，100 198，187，175 4 527 688 22.5 0.77 372，299，298 100，100，100 190，200，183 5 530 678 21 0.78 299，310，297 100，97，100 177，168，197 6 525 685 22 0.77 269，256，270 100，90，98 166，187，179 7 530 690 23 0.77 255，279，262 100，95，100 189，173，162

[0081] As can be seen from Tables 1 and 2, the production method of this invention adopts a low C content composition design. By adding Nb, Cr, and Mo in combination, and through a special rolling controlled cooling mode, a multiphase steel plate with bainitic + ferrite + martensite structure is obtained. This ensures that the strength, extremely low yield strength ratio, -60℃ low temperature impact, impact fiber ratio, and aging impact meet the requirements. These performance indicators can greatly improve the welding and assembly characteristics of the steel plate to adapt to the characteristics of high altitude and complex laying environment in western regions.

[0082] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for producing a thick Q500qF bridge deck with a thickness of 100mm, comprising the following partial chemical composition and mass percentage: C: 0.07%, Mn: 1.70%, Cr: 0.35%, P: 0.012%, S: 0.003%, Nb: 0.015%, Mo: 0.15%, with the remainder being Fe and unavoidable impurities, the sum of which is 100%. The production method for the aforementioned Q500qF bridge plate includes a production process comprising converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein: (1) LF+RH refining is used during refining to make the gas H content of the steel plate 0.5ppm and N content 35ppm; (2) Rolling process: roughing temperature 900℃, finishing temperature 700℃, water immersion temperature 630℃; (3) Controlled cooling process in rolling: The temperature of the steel plate when it turns red is limited to 400℃; (4) Heat treatment process: Tempering is carried out at 480℃ to eliminate surface stress of the steel plate; The produced bridge deck has a yield strength of 512 MPa, a tensile strength of 677 MPa, an elongation of 21%, a yield strength ratio of 0.76, and impact energy at -60℃ of 275 J, 289 J, and 295 J, with an average of 286.3 J. The fiber content of the impact section at -60℃ is 95%, 100%, and 100%, with an average of 98.3%. The impact energy at -60℃ with 5% deformation is 170 J, 200 J, and 212 J, with an average of 194 J.

2. A method for producing a thick Q500qF bridge deck with a thickness of 110mm, comprising the following partial chemical composition and mass percentage: C: 0.08%, Mn: 1.75%, Cr: 0.42%, P: 0.010%, S: 0.002%, Nb: 0.035%, Mo: 0.25%, with the remainder being Fe and unavoidable impurities, the sum of which is 100%. The production method for the aforementioned Q500qF bridge plate includes a production process comprising converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein: (1) LF+RH refining is used during refining to make the gas content of steel plate 0.4ppm and N content 32ppm; (2) Rolling process: roughing temperature 970℃, finishing temperature 710℃, water immersion temperature 600℃; (3) Controlled cooling process in rolling: The temperature of the steel plate when it turns red is limited to 420℃; (4) Heat treatment process: Tempering is carried out at a temperature of 490℃ to eliminate surface stress of the steel plate; The produced bridge deck has a yield strength of 522 MPa, a tensile strength of 685 MPa, an elongation of 22%, a yield-to-tensile ratio of 0.76, and impact energy at -60℃ of 300 J, 310 J, and 299 J, with an average of 303 J. The fiber content of the impact section at -60℃ is 100%, 100%, and 100%, with an average of 100%. The impact energy at -60℃ with 5% deformation is 199 J, 201 J, and 220 J, with an average of 206.7 J.

3. A method for producing a thick Q500qF bridge deck with a thickness of 125mm, wherein the partial chemical composition and mass percentage of the deck are as follows: C: 0.08%, Mn: 1.83%, Cr: 0.51%, P: 0.008%, S: 0.003%, Nb: 0.040%, Mo: 0.28%, with the remainder being Fe and unavoidable impurities, and the sum of the above components being 100%. The production method for the aforementioned Q500qF bridge plate includes a production process comprising converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein: (1) LF+RH refining is used during refining, so that the gas H content of the steel plate is 0.42ppm and the N content is 31ppm; (2) Rolling process: roughing temperature 960℃, finishing temperature 720℃, water immersion temperature 610℃; (3) Controlled cooling process in rolling: The reddening temperature of the steel plate is limited to 435℃; (4) Heat treatment process: Tempering is carried out at a temperature of 520℃ to eliminate surface stress of the steel plate; The produced bridge deck has a yield strength of 531 MPa, a tensile strength of 690 MPa, an elongation of 22%, a yield strength ratio of 0.77, and impact energy at -60℃ of 282 J, 301 J, and 288 J, with an average of 290.3 J. The fiber content of the impact section at -60℃ is 100%, 100%, and 100%, with an average of 100%. The impact energy at -60℃ with 5% deformation is 198 J, 187 J, and 175 J, with an average of 186.7 J.

4. A method for producing a thick Q500qF bridge deck with a thickness of 130mm, comprising the following partial chemical composition and mass percentage: C: 0.07%, Mn: 1.91%, Cr: 0.57%, P: 0.008%, S: 0.002%, Nb: 0.041%, Mo: 0.35%, with the remainder being Fe and unavoidable impurities, the sum of which is 100%. The production method for the aforementioned Q500qF bridge plate includes a production process comprising converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein: (1) LF+RH refining is used during refining to make the gas content of steel plate 0.35ppm H and 30ppm N; (2) Rolling process: roughing temperature 930℃, finishing temperature 720℃, water immersion temperature 600℃; (3) Controlled cooling process in rolling: The temperature of the steel plate when it turns red is limited to 470℃; (4) Heat treatment process: Tempering is carried out at a temperature of 540℃ to eliminate surface stress of the steel plate; The produced bridge deck has a yield strength of 527 MPa, a tensile strength of 688 MPa, an elongation of 22.5%, a yield strength ratio of 0.77, and impact energy at -60℃ of 372 J, 299 J, and 298 J, with an average of 323 J. The fiber content of the impact section at -60℃ is 100%, 100%, and 100%, with an average of 100%. The impact energy at -60℃ with 5% deformation is 190 J, 200 J, and 183 J, with an average of 191 J.

5. A method for producing a thick Q500qF bridge deck with a thickness of 140mm, wherein the partial chemical composition and mass percentage of the deck are as follows: C: 0.09%, Mn: 1.95%, Cr: 0.65%, P: 0.006%, S: 0.002%, Nb: 0.039%, Mo: 0.40%, with the remainder being Fe and unavoidable impurities, and the sum of the above components being 100%. The production method for the aforementioned Q500qF bridge plate includes a production process comprising converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein: (1) LF+RH refining is used during refining to make the gas content of steel plate 0.38ppm H and 30ppm N; (2) Rolling process: roughing temperature 920℃, finishing temperature 700℃, water immersion temperature 540℃; (3) Controlled cooling process in rolling: The temperature of the steel plate when it turns red is limited to 480℃; (4) Heat treatment process: Tempering is carried out at a temperature of 580℃ to eliminate surface stress of the steel plate; The produced bridge deck has a yield strength of 530 MPa, a tensile strength of 678 MPa, an elongation of 21%, a yield strength ratio of 0.78, and impact energy at -60℃ of 299 J, 310 J, and 297 J, with an average of 302 J. The fiber content of the impact section at -60℃ is 100%, 97%, and 100%, with an average of 99%. The impact energy at -60℃ with 5% deformation is 177 J, 168 J, and 197 J, with an average of 180.7 J.

6. A method for producing a thick Q500qF bridge deck with a thickness of 145mm, wherein the partial chemical composition and mass percentage of the deck are as follows: C: 0.11%, Mn: 1.97%, Cr: 0.68%, P: 0.010%, S: 0.002%, Nb: 0.042%, Mo: 0.41%, with the remainder being Fe and unavoidable impurities, and the sum of the above components being 100%. The production method for the aforementioned Q500qF bridge plate includes a production process comprising converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein: (1) LF+RH refining is used during refining to make the gas content of steel plate 0.45ppm and N content 25ppm; (2) Rolling process: roughing temperature 910℃, finishing temperature 710℃, water immersion temperature 510℃; (3) Controlled cooling process in rolling: The temperature of the steel plate when it turns red is limited to 480℃; (4) Heat treatment process: Tempering is carried out at a temperature of 590℃ to eliminate surface stress of the steel plate; The produced bridge deck has a yield strength of 525 MPa, a tensile strength of 685 MPa, an elongation of 22%, a yield strength ratio of 0.77, and impact energy at -60℃ of 269 J, 256 J, and 270 J, with an average of 265 J. The fiber content of the impact section at -60℃ is 100%, 90%, and 98%, with an average of 96%. The impact energy at -60℃ with 5% deformation is 166 J, 187 J, and 179 J, with an average of 177.3 J.

7. A method for producing a thick Q500qF bridge deck with a thickness of 150mm, wherein the partial chemical composition and mass percentage of the deck are as follows: C: 0.10%, Mn: 2.00%, Cr: 0.70%, P: 0.010%, S: 0.003%, Nb: 0.045%, Mo: 0.45%, with the remainder being Fe and unavoidable impurities, and the sum of the above components being 100%. The production method for the aforementioned Q500qF bridge plate includes a production process comprising converter smelting, refining, continuous casting, billet heating, rolling, and heat treatment, wherein: (1) LF+RH refining is used during refining to make the gas content of steel plate 0.36ppm H and 30ppm N; (2) Rolling process: roughing temperature 900℃, finishing temperature 700℃, water immersion temperature 500℃; (3) Controlled cooling process in rolling: The temperature of the steel plate when it turns red is limited to 490℃; (4) Heat treatment process: Tempering is carried out at 600℃ to eliminate surface stress of the steel plate; The produced bridge deck has a yield strength of 530 MPa, a tensile strength of 690 MPa, an elongation of 23%, a yield strength ratio of 0.77, and impact energy at -60℃ of 255 J, 279 J, and 262 J, with an average of 265.3 J. The fiber content of the impact section at -60℃ is 100%, 95%, and 100%, with an average of 98.3%. The impact energy at -60℃ with 5% deformation is 189 J, 173 J, and 162 J, with an average of 174.7 J.