An ultra-wide Q500qD bridge deck and its manufacturing process

Abstract

This invention discloses an ultra-wide Q500qD bridge plate and its manufacturing process, relating to the field of metallurgical technology. Its chemical composition and mass percentages are as follows: C: 0.09–0.11%, Mn: 1.60–1.65%, Cr: 0.55–0.70%, P≤0.012%, S≤0.010%, Nb: 0.035–0.045%, V: 0.001–0.007%, Ti: 0.020–0.035%, Mo: 0.05–0.09%, with the remainder being Fe and unavoidable impurities. This invention employs a low-C content composition design, adding Nb, Ti, Cr, and Mo in a composite manner, and using a special controlled-cooling rolling process to obtain a multiphase steel plate with a bainitic + ferrite + very low martensite microstructure. This ensures that the strength, extremely low yield strength ratio, -20℃ low-temperature impact resistance, impact fiber ratio, and aging impact resistance meet the requirements. Meanwhile, Q500qD steel plates produced by ordinary normalizing or quenching and tempering have a high yield strength ratio and a relatively small margin for impact toughness.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to an ultra-wide Q500qD bridge plate and its manufacturing process. Background Technology

[0002] High-strength bridge steel is increasingly being used in key national projects, especially in western regions. These areas are often remote, high-altitude regions with complex terrain. The steel used in these projects is complex, with high performance requirements, necessitating wide steel plates to reduce the amount of welding required for butt joints and lower construction difficulty. Furthermore, the complex environment in these areas necessitates careful consideration of bridge safety during design, requiring the development of wide, high-performance bridge plates to improve the steel's fracture toughness and seismic resistance. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an ultra-wide Q500qD bridge plate and its manufacturing process.

[0004] To solve the above technical problems, the technical solution of the present invention is as follows:

[0005] An ultra-wide Q500qD bridge plate has the following chemical composition and mass percentage: C: 0.09-0.11%, Mn: 1.60-1.65%, Cr: 0.55-0.70%, P≤0.012%, S≤0.010%, Nb: 0.035-0.045%, V: 0.001-0.007%, Ti: 0.020-0.035%, Mo: 0.05-0.09%, with the remainder being Fe and unavoidable impurities.

[0006] The present invention also provides a production process for ultra-wide Q500qD bridge plates, the production steps of which include smelting, rolling, controlled cooling and heat treatment in sequence.

[0007] As a preferred embodiment of the production process of the ultra-wide Q500qD bridge plate of the present invention, the smelting process includes: refining the billet using LF and RH refining processes to make the hydrogen content in the billet ≤1ppm and the nitrogen content ≤40ppm.

[0008] As a preferred embodiment of the production process of the ultra-wide Q500qD bridge plate of the present invention, the initial rolling temperature of the rolling process is 760-780℃, and the water immersion temperature is 650-680℃.

[0009] As a preferred embodiment of the production process of the ultra-wide Q500qD bridge plate of the present invention, the red-heating temperature in the controlled cooling process is 400-500℃.

[0010] As a preferred embodiment of the production process of the ultra-wide Q500qD bridge plate of the present invention, the tempering temperature in the heat treatment process is 480-510℃.

[0011] As a preferred embodiment of the production process of the ultra-wide Q500qD bridge plate of the present invention, the steel plate has a yield strength ≥500Mpa, a tensile strength of 630-750Mpa, an elongation ≥18%, an impact strength of ≥250J at -20℃, and a yield strength ratio ≤0.84.

[0012] As a preferred embodiment of the production process of the ultra-wide Q500qD bridge plate of the present invention, the steel plate has an impact cross-sectional fiber content ≥95% and an aging impact performance of ≥150J with 5% deformation.

[0013] As a preferred embodiment of the production process of the ultra-wide Q500qD bridge plate of the present invention, the steel plate has a thickness of 8-50mm and a width of 4200-4700mm.

[0014] The beneficial effects of this invention are:

[0015] This invention employs a low-carbon composition design, incorporating Nb, Ti, Cr, and Mo in a composite manner, and utilizing a special controlled-cooling rolling process to obtain a multiphase steel plate with a bainitic, ferrite, and minimal martensite microstructure. This ensures that the required strength, extremely low yield strength ratio, -20°C low-temperature impact resistance, impact fiber content, and aging impact resistance are met. Meanwhile, Q500qD steel plates produced by ordinary normalizing or quenching and tempering exhibit a high yield strength ratio but a relatively small margin in impact toughness. Detailed Implementation

[0016] To make the content of this invention easier to understand, the invention will be further described in detail below based on specific embodiments.

[0017] This application provides an ultra-wide Q500qD bridge plate with the following chemical composition and mass percentage: C: 0.09-0.11%, Mn: 1.60-1.65%, Cr: 0.55-0.70%, P≤0.012%, S≤0.010%, Nb: 0.035-0.045%, V: 0.001-0.007%, Ti: 0.020-0.035%, Mo: 0.05-0.09%, with the remainder being Fe and unavoidable impurities.

[0018] This application also provides a manufacturing process for an ultra-wide Q500qD bridge plate, which includes smelting, rolling, controlled cooling, and heat treatment in sequence.

[0019] The aforementioned smelting process includes: refining the billet using LF and RH refining processes to ensure that the hydrogen content in the billet is ≤1ppm and the nitrogen content is ≤40ppm. The initial rolling temperature of the aforementioned rolling process is 760-780℃, and the water immersion temperature is 650-680℃. The reheating temperature in the aforementioned controlled cooling process is 400-500℃. The tempering temperature in the aforementioned heat treatment process is 480-510℃.

[0020] The following is an illustration through specific examples:

[0021] Example 1: This example provides a method for producing an ultra-wide Q500qD bridge plate with a thickness of 8mm and a width of 4200mm. Its chemical composition and mass percentage are shown in Table 1.

[0022] This embodiment also provides a production method for ultra-wide Q500qD bridge plates, which uses LF and RH refining technology during smelting to ensure that the gas H content of the steel plate is 0.8ppm and the N content is 35ppm.

[0023] Furthermore, the production method of the ultra-wide Q500qD bridge plate provided in this embodiment includes rolling, controlled cooling, and heat treatment processes in sequence, and the specific process steps are as follows:

[0024] (1) Rolling process: the initial rolling temperature of the steel plate is 780℃, and the water immersion temperature is 650℃.

[0025] (2) Controlled cooling process: The temperature of the steel plate when it turns red is limited to 400℃

[0026] (3) Heat treatment process: Tempering is carried out at 480℃ to eliminate surface stress of steel plate.

[0027] The mechanical properties of the ultra-wide Q500qD bridge deck obtained in this implementation are shown in Table 2.

[0028] Example 2: This example provides a method for producing an ultra-wide Q500qD bridge plate with a thickness of 16mm and a width of 4500mm. Its chemical composition and mass percentage are shown in Table 1.

[0029] This embodiment also provides a production method for ultra-wide Q500qD bridge plates, which uses LF and RH refining technology during smelting to ensure that the gas H content of the steel plate is 0.7ppm and the N content is 37ppm.

[0030] Furthermore, the production method of the ultra-wide Q500qD bridge plate provided in this embodiment includes rolling, controlled cooling, and heat treatment processes in sequence, and the specific process steps are as follows:

[0031] (1) Rolling process: the initial rolling temperature of the steel plate is 770℃, and the water immersion temperature is 660℃.

[0032] (2) Controlled cooling process: The reddening temperature of the steel plate is limited to 420℃.

[0033] (3) Heat treatment process: Tempering is carried out at a temperature of 485℃ to eliminate surface stress of the steel plate.

[0034] The mechanical properties of the ultra-wide Q500qD bridge deck obtained in this implementation are shown in Table 2.

[0035] Example 3: This example provides a method for producing an ultra-wide Q500qD bridge plate with a thickness of 22mm and a width of 4550mm. Its chemical composition and mass percentage are shown in Table 1.

[0036] This embodiment also provides a production method for ultra-wide Q500qD bridge plates, which uses LF and RH refining technology during smelting to ensure that the gas H content of the steel plate is 0.8ppm and the N content is 31ppm.

[0037] Furthermore, the production method of the ultra-wide Q500qD bridge plate provided in this embodiment includes rolling, controlled cooling, and heat treatment processes in sequence, and the specific process steps are as follows:

[0038] (1) Rolling process: the initial rolling temperature of the steel plate is 760℃, and the water immersion temperature is 670℃.

[0039] (2) Controlled cooling process: The reddening temperature of the steel plate is limited to 435℃.

[0040] (3) Heat treatment process: Tempering is carried out at 490℃ to eliminate surface stress of steel plate.

[0041] The mechanical properties of the ultra-wide Q500qD bridge deck obtained in this implementation are shown in Table 2.

[0042] Example 4: This example provides a method for producing an ultra-wide Q500qD bridge plate with a thickness of 28mm and a width of 4620mm. Its chemical composition and mass percentage are shown in Table 1.

[0043] This embodiment also provides a production method for ultra-wide Q500qD bridge plates, which uses LF and RH refining technology during smelting to ensure that the gas H content of the steel plate is 0.5ppm and the N content is 30ppm.

[0044] Furthermore, this embodiment provides a method for producing an ultra-wide Q500qD bridge plate, which includes rolling, controlled cooling, and heat treatment processes in sequence. The specific process steps are as follows:

[0045] (1) Rolling process: the initial rolling temperature of the steel plate is 765℃, and the water immersion temperature is 670℃.

[0046] (2) Controlled cooling process: The reddening temperature of the steel plate is limited to 470℃.

[0047] (3) Heat treatment process: Tempering is carried out at 490℃ to eliminate surface stress of steel plate.

[0048] The mechanical properties of the ultra-wide Q500qD bridge deck obtained in this implementation are shown in Table 2.

[0049] Example 5: This example provides a method for producing an ultra-wide Q500qD bridge plate with a thickness of 32mm and a width of 4600mm. Its chemical composition and mass percentage are shown in Table 1.

[0050] This embodiment also provides a production method for ultra-wide Q500qD bridge plates, which uses LF and RH refining technology during smelting to ensure that the gas H content of the steel plate is 0.8ppm and the N content is 30ppm.

[0051] Furthermore, this embodiment provides a method for producing an ultra-wide Q500qD bridge plate, which includes rolling, controlled cooling, and heat treatment processes in sequence. The specific process steps are as follows:

[0052] (1) Rolling process: the initial rolling temperature of the steel plate is 755℃, and the water immersion temperature is 680℃.

[0053] (2) Controlled cooling process: The temperature of the steel plate when it turns red is limited to 480℃

[0054] (3) Heat treatment process: Tempering is carried out at 500℃ to eliminate surface stress of steel plate.

[0055] The mechanical properties of the ultra-wide Q500qD bridge deck obtained in this implementation are shown in Table 2.

[0056] Example 6: This example provides a method for producing an ultra-wide Q500qD bridge plate with a thickness of 44mm and a width of 4650mm. Its chemical composition and mass percentage are shown in Table 1.

[0057] This embodiment provides a production method for ultra-wide Q500qD bridge plates, which employs LF and RH refining technologies during smelting to ensure that the gaseous H content of the steel plate is 0.5ppm and the N content is 39ppm.

[0058] Furthermore, the production method of the ultra-wide Q500qD bridge plate provided in this embodiment includes rolling, controlled cooling, and heat treatment processes in sequence, and the specific process steps are as follows:

[0059] (1) Rolling process: the initial rolling temperature of the steel plate is 760℃, and the water immersion temperature is 660℃.

[0060] (2) Controlled cooling process: The temperature of the steel plate when it turns red is limited to 480℃

[0061] (3) Heat treatment process: Tempering is carried out at 500℃ to eliminate surface stress of steel plate.

[0062] The mechanical properties of the ultra-wide Q500qD bridge deck obtained in this implementation are shown in Table 2.

[0063] Example 7: This example provides a method for producing an ultra-wide Q500qD bridge plate with a thickness of 48mm and a width of 4700mm. Its chemical composition and mass percentage are shown in Table 1.

[0064] This embodiment also provides a production method for ultra-wide Q500qD bridge plates, which uses LF and RH refining technology during smelting to ensure that the gas H content of the steel plate is 0.6ppm and the N content is 38ppm.

[0065] Furthermore, the production method of the ultra-wide Q500qD bridge plate provided in this embodiment includes rolling, controlled cooling, and heat treatment processes in sequence, and the specific process steps are as follows:

[0066] (1) Rolling process: the initial rolling temperature of the steel plate is 780℃, and the water immersion temperature is 670℃.

[0067] (2) Controlled cooling process: The reddening temperature of the steel plate is limited to 490℃.

[0068] (3) Heat treatment process: Tempering is carried out at 490℃ to eliminate surface stress of steel plate.

[0069] The mechanical properties of the ultra-wide Q500qD bridge deck obtained in this implementation are shown in Table 2.

[0070] Example 8: This example describes a method for producing an ultra-wide Q500qD bridge deck with a thickness of 50mm and a width of 4700mm. Its chemical composition and mass percentage are shown in Table 1.

[0071] This embodiment also provides a production method for ultra-wide Q500qD bridge plates, which uses LF and RH refining technology during smelting to ensure that the gas H content of the steel plate is 0.9ppm and the N content is 37ppm.

[0072] Furthermore, the production method of the ultra-wide Q500qD bridge plate provided in this embodiment includes, in sequence, rolling, controlled cooling, and heat treatment processes, the specific process steps of which are as follows:

[0073] (1) Rolling process: the initial rolling temperature of the steel plate is 780℃, and the water immersion temperature is 650℃.

[0074] (2) Controlled cooling process: The temperature of the steel plate when it turns red is limited to 500℃

[0075] (3) Heat treatment process: Tempering is carried out at 490℃ to eliminate surface stress of steel plate.

[0076] The mechanical properties of the ultra-wide Q500qD bridge deck obtained in this implementation are shown in Table 2.

[0077]

[0078] Table 1 Chemical composition of steel plates in Examples 1-8

[0079]

[0080] Table 2 Mechanical property data of steel plates in Examples 1-8

[0081] As can be seen from the above examples: First, the steel plate production width is 4200-4700mm, far exceeding the design width of ordinary bridge plates. Second, the steel plate has an elongation rate ≥18%, an impact strength of ≥250J at -20℃, a yield strength ratio ≤0.84, an impact cross-sectional fiber content ≥95%, and an aging impact performance of ≥150J with 5% deformation. These indicators can significantly improve the welding and assembly characteristics of the steel plate, adapting to the high altitude and complex laying environment of western regions. Furthermore, the adoption of low-carbon and multiphase microstructure design effectively improves the seismic safety factor.

[0082] Therefore, the technical solution of this application adopts a low-C content composition design, and through the addition of Nb, Ti, Cr, and Mo composites, and employs a special rolling controlled cooling mode, a multiphase steel plate with bainitic + ferrite + very little martensite is obtained, ensuring that the strength, extremely low yield strength ratio, -20℃ low-temperature impact, impact fiber ratio, and aging impact meet the requirements. Meanwhile, Q500qD steel plates produced by ordinary normalizing or quenching and tempering have a high yield strength ratio and a relatively small margin for impact toughness.

[0083] In addition to the above embodiments, the present invention may have other implementation methods; all technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A manufacturing process for an ultra-wide Q500qD bridge deck, characterized in that: The chemical composition and mass percentage of the ultra-wide Q500qD bridge plate are as follows: C: 0.09-0.11%, Mn: 1.60-1.65%, Cr: 0.55-0.70%, P≤0.012%, S≤0.010%, Nb: 0.035-0.045%, V: 0.001-0.007%, Ti: 0.020-0.035%, Mo: 0.05-0.09%, with the remainder being Fe and unavoidable impurities; The production process of the ultra-wide Q500qD bridge plate includes smelting, rolling, controlled cooling, and heat treatment in sequence. The smelting process includes: refining using LF and RH refining processes to make the hydrogen content in the billet ≤1ppm and the nitrogen content ≤40ppm; The initial rolling temperature of the rolling process is 760-780℃; The water inlet temperature in the controlled cooling process is 650-680℃, and the reddening temperature is 400-500℃; Tempering heat treatment is performed at a temperature of 480-510℃; The bridge deck has a yield strength ≥500 MPa, tensile strength 630-750 MPa, elongation ≥18%, impact strength at -20℃ ≥250 J, and yield strength ratio ≤0.

84. The bridge deck has an impact cross-sectional fiber content of ≥95% and an aging impact performance of ≥150J with 5% deformation. The bridge deck has a thickness of 8-50mm and a width of 4200-4700mm.

Images