Cr-Cu-series corrosion-resistant and weather-resistant 635MPa reinforcing steel bar and smelting production method

Abstract

The invention relates to the technical field of steel bar smelting, and discloses a Cr-Cu series corrosion-resistant weather-resistant 635MPa steel bar, which comprises the following chemical components (by mass fraction): 0.15-0.20% of C; 0.70% to 0.80% of Si; mn: 1.30 to 1.60%; p: less than or equal to 0.035%; s: less than or equal to 0.035%; 1.0 to 2.0 percent of Cr; 0.5 to 0.6 percent of Cu; 0.020% to 0.030% of Nb; according to the method, high strength and high corrosion resistance are synergistically improved, through the synergistic effect of Cr (1.0-2.0%) and Cu (0.5-0.6%), a compact chromic oxide film and a stable passivation layer are formed, Cl <-> permeation is prevented, the corrosion resistance is improved by 2-3 times compared with common steel bars, and the requirements of severe environments such as ocean and industrial corrosion are met; microalloy elements Nb (0.020-0.030%) and V (0.050-0.080%) are subjected to grain refinement (the grain size is smaller than or equal to 10 microns) and precipitation strengthening (such as VC and NbC), so that the yield strength of the steel bar reaches 665 MPa, the tensile strength reaches 877 MPa, the yield-strength ratio is 1.32, and the requirements of GB / T 1499.2-2018 aseismic steel bars are met.

Description

Technical Field

[0001] The present invention relates to the technical field of steel bar smelting, in particular to Cr-Cu series corrosion-resistant and weather-resistant 635MPa steel bars and a smelting production method. Background Art

[0002] In the construction industry, the corrosion resistance and strength of steel bars are key factors affecting structural durability. Conventional steel bars are susceptible to chloride ion corrosion in harsh environments such as humidity and salt spray, leading to rust and expansion, decreased strength, and a shortened service life. While conventional HRB-series steel bars meet mechanical performance requirements, their corrosion resistance is insufficient, requiring an additional anti-corrosion coating, which increases costs and complicates the process.

[0003] At the same time, the smelting of high-strength steel bars (such as 635MPa grade) faces the dual challenges of composition control and organizational optimization: Insufficient corrosion resistance: Traditional alloying elements (such as C and Mn) are difficult to achieve both high strength and corrosion resistance. - The erosion causes the oxide film on the surface of the steel bar to be destroyed, triggering electrochemical corrosion.

[0004] Mechanical property limitations: Simply relying on carbon content to increase strength will reduce toughness and welding performance, making it difficult to meet seismic design requirements.

[0005] Extensive smelting process: The existing rolling process is difficult to accurately control the grain size and structural uniformity, resulting in insufficient strength-to-yield ratio, low production efficiency and high energy consumption.

[0006] Therefore, there is an urgent need to develop a steel bar with both high strength and high corrosion resistance and an efficient smelting method thereof to solve the durability problem of traditional steel bars in harsh environments, reduce maintenance costs, and improve project safety. Summary of the Invention

[0007] (1) Technical problems solved In response to the shortcomings of the existing technology, the present invention provides Cr-Cu corrosion-resistant and weather-resistant 635MPa steel bars and a smelting production method, which have the advantages of synergistic improvement of high strength and high corrosion resistance, and solve the problems of insufficient corrosion resistance and extensive smelting process.

[0008] (2) Technical solution In order to achieve the above-mentioned purpose of synergistically improving high strength and high corrosion resistance, the present invention provides the following technical solution: Cr-Cu series corrosion-resistant and weather-resistant 635MPa steel bar, including the following chemical components (mass fraction): C: 0.15-0.20%; Si: 0.70-0.80%; Mn: 1.30-1.60%; P: ≤0.035%; S: ≤0.035%; Cr: 1.0-2.0%; Cu: 0.5-0.6%; Nb: 0.020-0.030%; V: 0.050-0.080%.

[0009] Preferably, the Cr forms a dense chromium oxide film to prevent Cl - Erosion, improve corrosion resistance; improve strength through solid solution strengthening and precipitation strengthening.

[0010] Preferably, the Cu improves the properties of the passivation film, promotes the formation of the oxide film, and cooperates with Cr to enhance the corrosion resistance; and improves the low-temperature toughness and heat treatment performance.

[0011] Preferably, the Nb+V refines grains, improves grain boundary structure, enhances strength and toughness through microalloy strengthening mechanism, and optimizes welding performance.

[0012] Preferably, the Cr-Cu series corrosion-resistant and weather-resistant 635MPa steel bar smelting production method includes the following method steps S1 converter steelmaking: End point control: The final carbon content is controlled at 0.08-0.15%, and the phosphorus content is ≤0.015%; Adopt slag blocking steel tapping process to reduce the slag brought in; Among them, in S1 converter steelmaking, the order of alloy addition is: Add lime (slagging agent) when 1 / 5 of the steel is tapped; When 3 / 4 of the steel is tapped, add: ① Slag (to adjust slag basicity); ② Silicon manganese alloy (adjust Si and Mn content); ③ Medium carbon ferrochrome, nickel plate, copper tube, vanadium nitrogen alloy, ferroniobium (introducing Cr, Ni, Cu, V, Nb elements); ④ Recarburizer (to adjust carbon content to the target range); S2LF furnace refining: Bottom argon blowing process: argon is blown from the bottom throughout the process, with the flow rate being based on the standard of no splashing of molten steel, thus promoting the floating of inclusions; Slag making system: add lime and wollastonite, control slag basicity R=1.5-2.1, slag making time ≥12 minutes; Composition adjustment: Based on the composition analysis before entering the station, alloys are added before and during refining to accurately adjust the content of Si, Mn, V, Nb, Cr, and Cu; S3VD Vacuum Degassing: Vacuum treatment: maintain the vacuum degree at 15-30Pa for ≥15 minutes to reduce the gas content (H, N) in the steel; Final blowing treatment: Soft blowing of argon for ≥15 minutes before leaving the station to further purify the molten steel; S4165 billet continuous casting: Protective casting: Ladle → Tundish: Use protective sleeve + argon seal to prevent molten steel from oxidation; Tundish: Use molten steel covering agent and argon blowing protection to reduce liquid level fluctuation; Tundish → crystallizer: use submerged nozzle to avoid secondary oxidation; Cooling system: Primary cooling: water flow 110-125m 3 / h, rapid solidification of the surface; Secondary cooling: specific water volume 0.35-0.40L / kg, weak cooling process controls the thickness of surface acicular ferrite; S5 rolling process: Heating furnace control: heating and holding time ≥ 120 minutes to ensure full dissolution of alloy elements and uniform heating temperature; Rolling in stages: Rough and medium rolling stage: rolling temperature 1050-1100℃, using the alternating effects of recrystallization and deformation to refine the austenite grains; Finishing rolling stage: turn off the water cooling device to avoid cracks caused by rapid cooling of the surface; air cooling after rolling promotes the precipitation of micro-alloy carbides and refines the structure; S6 follow-up processing: Cut into sections → Cool naturally on cooling bed → Cold cut to length → Remove short lengths → Count and finish → Bundle and weigh → Store in warehouse.

[0013] Preferably, the S2LF furnace refining and soft argon blowing treatment: soft argon blowing for ≥10 minutes before leaving the station to ensure uniform composition and reduce inclusions.

[0014] Preferably, the casting parameters of the S4165 billet continuous casting are: Superheat 15-25℃, casting speed 2.1-2.5m / min (low speed casting), stabilize the liquid level, casting speed and superheat to avoid casting defects.

[0015] (3) Beneficial effects Compared with the prior art, the present invention provides a Cr-Cu series corrosion-resistant and weather-resistant 635MPa steel bar and a smelting production method, which has the following beneficial effects: 1. This Cr-Cu series corrosion-resistant and weather-resistant 635MPa steel bar and its smelting production method achieves a synergistic improvement in high strength and high corrosion resistance: Through the synergistic effect of Cr (1.0-2.0%) and Cu (0.5-0.6%), a dense chromium oxide film and a stable passivation layer are formed to prevent Cl - The corrosion resistance is 2-3 times higher than that of ordinary steel bars, meeting the requirements of harsh environments such as marine and industrial corrosion. Microalloying elements Nb (0.020-0.030%) and V (0.050-0.080%) contribute to grain refinement (grain size ≤ 10 μm) and precipitation strengthening (such as VC and NbC), resulting in a steel bar yield strength of 665 MPa, a tensile strength of 877 MPa, and a strength-to-yield ratio of 1.32, meeting the requirements of GB / T 1499.2-2018 for seismic-resistant steel bars.

[0016] 2. The Cr-Cu series corrosion-resistant and weather-resistant 635MPa steel bar and its smelting production method achieve high efficiency and energy saving in the smelting process: Precision temperature-controlled rolling: Through recrystallization control in the roughing and intermediate rolling stages (1050-1100°C) and air cooling after rolling, surface cracks caused by water cooling are avoided, while promoting the uniform precipitation of micro-alloying elements and reducing energy consumption by about 15%; Low-damage continuous casting technology: Using full argon seal protection casting and weak cooling process (secondary cooling water volume 0.35-0.40L / kg), it reduces molten steel oxidation and ingot defects, and increases the yield rate to over 98%; Precise composition control: LF furnace refining and VD vacuum degassing processes achieve a composition deviation of ≤±0.02% and gas content (H≤2ppm, N≤80ppm), improving the purity and service stability of the steel bars.

[0017] 3. The Cr-Cu series corrosion-resistant and weather-resistant 635MPa steel bar and its smelting production method achieves cost and environmental advantages: Eliminate the need for additional anti-corrosion coating, reducing material costs by approximately 20%; Process integration reduces equipment investment and energy consumption, and reduces carbon emissions per unit of steel bars by 10%, which is in line with the development trend of green building materials. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] This proposal provides a technical solution, specifically, Cr-Cu series corrosion-resistant and weather-resistant 635MPa steel bars, including the following chemical composition (mass fraction): C: 0.15-0.20%; Si: 0.70-0.80%; Mn: 1.30-1.60%; P: ≤0.035%; S: ≤0.035%; Cr: 1.0-2.0%; Cu: 0.5-0.6%; Nb: 0.020-0.030%; V: 0.050-0.080%; Core role: Cr: forms a dense chromium oxide film to prevent Cl - Erosion, improve corrosion resistance; improve strength through solid solution strengthening and precipitation strengthening; Cu: Improves the properties of the passivation film, promotes the formation of oxide film, and synergizes with Cr to enhance corrosion resistance; improves low-temperature toughness and heat treatment performance; Nb+V: refines grains, improves grain boundary structure, enhances strength and toughness through microalloy strengthening mechanism, and optimizes welding performance; Furthermore, the Cr-Cu series corrosion-resistant and weather-resistant 635MPa steel bar smelting production method includes the following method steps: S1 converter steelmaking: End point control: The final carbon content is controlled at 0.08-0.15%, and the phosphorus content is ≤0.015%; Adopt slag blocking steel tapping process to reduce the slag brought in; Among them, in S1 converter steelmaking, the order of alloy addition is: Add lime (slagging agent) when 1 / 5 of the steel is tapped; When 3 / 4 of the steel is tapped, add: ① Slag (to adjust slag basicity); ② Silicon manganese alloy (adjust Si and Mn content); ③ Medium carbon ferrochrome, nickel plate, copper tube, vanadium nitrogen alloy, ferroniobium (introducing Cr, Ni, Cu, V, Nb elements); ④ Recarburizer (to adjust carbon content to the target range); S2LF furnace refining: Bottom argon blowing process: argon is blown from the bottom throughout the process, with the flow rate being based on the standard of no splashing of molten steel, thus promoting the floating of inclusions; Slag making system: add lime and wollastonite, control slag basicity R=1.5-2.1, slag making time ≥12 minutes; Composition adjustment: Based on the composition analysis before entering the station, alloys are added before and during refining to accurately adjust the content of Si, Mn, V, Nb, Cr, and Cu; Among them, S2LF furnace refining, soft argon blowing treatment: soft argon blowing ≥ 10 minutes before leaving the station to ensure uniform composition and reduce inclusions; S3VD Vacuum Degassing: Vacuum treatment: maintain the vacuum degree at 15-30Pa for ≥15 minutes to reduce the gas content (H, N) in the steel; Final blowing treatment: Soft blowing of argon for ≥15 minutes before leaving the station to further purify the molten steel; S4165 billet continuous casting: Protective casting: Ladle → Tundish: Use protective sleeve + argon seal to prevent molten steel from oxidation; Tundish: Use molten steel covering agent and argon blowing protection to reduce liquid level fluctuation; Tundish → crystallizer: use submerged nozzle to avoid secondary oxidation; Cooling system: Primary cooling: water flow 110-125m 3 / h, rapid solidification of the surface; Secondary cooling: specific water volume 0.35-0.40L / kg, weak cooling process controls the thickness of surface acicular ferrite; Among them, the casting parameters of S4165 billet continuous casting are: Superheat 15-25℃, casting speed 2.1-2.5m / min (low speed casting), stabilize the liquid level, casting speed and superheat to avoid casting defects; S5 rolling process: Heating furnace control: heating and holding time ≥ 120 minutes to ensure full dissolution of alloy elements and uniform heating temperature; Rolling in stages: Rough and medium rolling stage: rolling temperature 1050-1100℃, using the alternating effects of recrystallization and deformation to refine the austenite grains; Finishing rolling stage: turn off the water cooling device to avoid cracks caused by rapid cooling of the surface; air cooling after rolling promotes the precipitation of micro-alloy carbides and refines the structure; S6 follow-up processing: Cut into sections → Cool naturally on cooling bed → Cold cut to length → Remove short lengths → Count and finish → Bundle and weigh → Store in warehouse.

[0020] In the present invention, combined with chemical composition regulation, according to the different rolling speeds and reductions of the roughing, medium and finishing rolling mills, the microalloy fine grain strengthening and solid solution strengthening mechanisms are utilized, and through a continuous temperature control + deformation rolling process, the refinement and homogenization of the steel microstructure are achieved. During the hot rolling process, the main core technology is divided into two stages according to the deformation temperature: ① Heating and holding time in the heating furnace for at least 120 minutes, and rolling within the rolling temperature range (1050~1100℃) during the rough and medium rolling processes, so that recrystallization and deformation are carried out alternately to refine the austenite grains; ② The water cooling device of the rolling line is turned off throughout the rolling process to avoid local overcooling and causing micro cracks on the steel surface. At the same time, air cooling is carried out after rolling to ensure the precipitation of microalloying elements and guarantee the structure and strength.

[0021] Implementation case: 1. Chemical composition and mechanical properties, please refer to the table below:

[0022] 2. Corrosion and weather resistance: The main factors affecting corrosion resistance and weathering resistance are the Cr content and Cu content of steel, while at the same time, it must have a very low C content. This patent refers to relevant domestic and foreign literature and rationally designs the chemical composition to ensure that the C content of the finished product does not exceed 0.20%, the Cr content is above 1.0%, and at the same time, 0.5-0.6% Cu content is added as an auxiliary, achieving a balance between corrosion resistance and steel cost. In addition to meeting the mechanical properties of conventional steel bars, it also has high corrosion resistance and weathering resistance. Through weekly immersion accelerated corrosion tests, marine environment exposure tests, marine environment tests of concrete blocks, and chloride ion corrosion resistance tests under simulated concrete pore fluid conditions, it is proved that the corrosion resistance of the steel bars is about 2-3 times higher than that of ordinary steel bars.

[0023] Furthermore, this method achieves a synergistic improvement in high strength and high corrosion resistance: Through the synergistic effect of Cr (1.0-2.0%) and Cu (0.5-0.6%), a dense chromium oxide film and a stable passivation layer are formed to prevent Cl - The corrosion resistance is 2-3 times higher than that of ordinary steel bars, meeting the requirements of harsh environments such as marine and industrial corrosion. Microalloying elements Nb (0.020-0.030%) and V (0.050-0.080%) contribute to grain refinement (grain size ≤ 10 μm) and precipitation strengthening (e.g., VC, NbC), resulting in a yield strength of 665 MPa, a tensile strength of 877 MPa, and a strength-to-yield ratio of 1.32, meeting the requirements of GB / T 1499.2-2018 for seismic reinforcement. Furthermore, the method achieves high efficiency and energy saving in the smelting process: Precision temperature-controlled rolling: Through recrystallization control in the roughing and intermediate rolling stages (1050-1100°C) and air cooling after rolling, surface cracks caused by water cooling are avoided, while promoting the uniform precipitation of micro-alloying elements and reducing energy consumption by about 15%; Low-damage continuous casting technology: Using full argon seal protection casting and weak cooling process (secondary cooling water volume 0.35-0.40L / kg), it reduces molten steel oxidation and ingot defects, and increases the yield rate to over 98%; Precise composition control: LF furnace refining and VD vacuum degassing processes achieve a composition deviation of ≤±0.02% and gas content (H≤2ppm, N≤80ppm), improving the purity and service stability of the steel bars. Furthermore, this method achieves cost and environmental advantages: Eliminate the need for additional anti-corrosion coating, reducing material costs by approximately 20%; Process integration reduces equipment investment and energy consumption, and reduces carbon emissions per unit of steel bars by 10%, which is in line with the development trend of green building materials.

[0024] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. Cr-Cu corrosion-resistant and weather-resistant 635MPa steel bar, characterized by: Includes the following chemical components (mass fraction): C：0.15-0.20%； Si: 0.70-0.80%; Mn: 1.30-1.60%; P：≤0.035%； S：≤0.035%； Cr：1.0-2.0%； Cu: 0.5-0.6%; Nb: 0.020-0.030%; V：0.050-0.080%。 2. The Cr-Cu corrosion-resistant and weather-resistant 635MPa steel bar according to claim 1, characterized in that: The Cr: forms a dense chromium oxide film to prevent Cl - Erosion, improve corrosion resistance; improve strength through solid solution strengthening and precipitation strengthening.

3. The Cr-Cu corrosion-resistant and weather-resistant 635MPa steel bar according to claim 1, characterized in that: The Cu improves the properties of the passivation film, promotes the formation of the oxide film, and cooperates with Cr to enhance the corrosion resistance; and improves the low-temperature toughness and heat treatment performance.

4. The Cr-Cu corrosion-resistant and weather-resistant 635MPa steel bar according to claim 1, characterized in that: The Nb+V: refines grains, improves grain boundary structure, increases strength and toughness through microalloy strengthening mechanism, and optimizes welding performance.

5. A method for smelting and producing Cr-Cu corrosion-resistant and weather-resistant 635MPa steel bars, characterized by: The method comprises the following steps S1: converter steelmaking: End point control: The final carbon content is controlled at 0.08-0.15%, and the phosphorus content is ≤0.015%; Adopt slag blocking steel tapping process to reduce the slag brought in; Among them, in S1 converter steelmaking, the order of alloy addition is: Add lime (slagging agent) when 1 / 5 of the steel is tapped; When 3 / 4 of the steel is tapped, add: ① Slag (to adjust slag basicity); ② Silicon manganese alloy (adjust Si and Mn content); ③ Medium carbon ferrochrome, nickel plate, copper tube, vanadium nitrogen alloy, ferroniobium (introducing Cr, Ni, Cu, V, Nb elements); ④ Recarburizer (to adjust carbon content to the target range); S2LF furnace refining: Bottom argon blowing process: argon is blown from the bottom throughout the process, with the flow rate being based on the standard of no splashing of molten steel, thus promoting the floating of inclusions; Slag making system: add lime and wollastonite, control slag basicity R=1.5-2.1, slag making time ≥12 minutes; Composition adjustment: Based on the composition analysis before entering the station, alloys are added before and during refining to accurately adjust the content of Si, Mn, V, Nb, Cr, and Cu; S3VD Vacuum Degassing: Vacuum treatment: maintain the vacuum degree at 15-30Pa for ≥15 minutes to reduce the gas content (H, N) in the steel; Final blowing treatment: Soft blowing of argon for ≥15 minutes before leaving the station to further purify the molten steel; S4165 billet continuous casting: Protective casting: Ladle → Tundish: Use protective sleeve + argon seal to prevent molten steel from oxidation; Tundish: Use molten steel covering agent and argon blowing protection to reduce liquid level fluctuation; Tundish → crystallizer: use submerged nozzle to avoid secondary oxidation; Cooling system: Primary cooling: water flow 110-125m 3 / h, rapid solidification of the surface; Secondary cooling: specific water volume 0.35-0.40L / kg, weak cooling process controls the thickness of surface acicular ferrite; S5 rolling process: Heating furnace control: heating and holding time ≥ 120 minutes to ensure full dissolution of alloy elements and uniform heating temperature; Rolling in stages: Rough and medium rolling stage: rolling temperature 1050-1100℃, using the alternating effects of recrystallization and deformation to refine the austenite grains; Finishing rolling stage: turn off the water cooling device to avoid cracks caused by rapid cooling of the surface; air cooling after rolling promotes the precipitation of micro-alloy carbides and refines the structure; S6 follow-up processing: Cut into sections → Cool naturally on cooling bed → Cold cut to length → Remove short lengths → Count and finish → Bundle and weigh → Store in warehouse.

6. The smelting and production method of Cr-Cu corrosion-resistant and weather-resistant 635MPa steel bars according to claim 5, characterized in that: The S2LF furnace refining and soft argon blowing treatment: soft argon blowing for ≥10 minutes before leaving the station to ensure uniform composition and reduce inclusions.

7. The smelting and production method of Cr-Cu corrosion-resistant and weather-resistant 635MPa steel bars according to claim 5, characterized in that: The casting parameters of the S4165 billet continuous casting are: Superheat 15-25℃, casting speed 2.1-2.5m / min (low speed casting), stabilize the liquid level, casting speed and superheat to avoid casting defects.

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