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CN-120555873-B - Hot-rolled wire rod for ultra-high strength bridge cable and production method thereof

CN120555873BCN 120555873 BCN120555873 BCN 120555873BCN-120555873-B

Abstract

The invention particularly discloses a hot rolled wire rod for an ultra-high strength bridge cable and a production method thereof, which sequentially comprise the steps of smelting, continuous casting, rolling, salt bath isothermal treatment, coil collecting and slow cooling treatment, wherein continuous casting billets with required components and proportions are obtained through the smelting and continuous casting steps, wires are wire-poured into the wire rod at the temperature of 880-920 ℃, the wire rod after wire-pouring is directly immersed into a salt bath at the temperature of 200-300 ℃ for isothermal treatment, medium-carbon martensite and non-transformed austenite are obtained, the wire rod after the salt bath treatment is immediately collected and coiled, and enters a constant-temperature annealing furnace at the temperature of 380-420 ℃ for slow cooling treatment at the temperature of not lower than 180 ℃ so that carbon elements in the martensite are diffused into the non-transformed austenite to obtain a small amount of bainite and residual austenite. The wire rod of the invention is used for manufacturing bridge cable wires, the wire rod is only required to be subjected to surface treatment, zinc/aluminum plating is carried out after 1-2 times of drawing, the strength of the wire rod reaches 2000-2100MPa, and the torsion times of the finished wire rod are not less than 12 times.

Inventors

  • LI YANG
  • XU CHUNFENG
  • HUANG ZHEN
  • GAO FENGSHAN
  • Chen Qianglei
  • LI JIE

Assignees

  • 青岛特殊钢铁有限公司

Dates

Publication Date
20260512
Application Date
20250429

Claims (8)

  1. 1. A production method of a hot-rolled wire rod for an ultra-high strength bridge cable is characterized in that the hot-rolled wire rod for the ultra-high strength bridge cable comprises the following chemical components ：C：0.24-0.36wt.％;Si：1.50-2.50wt.％;Mn：1.50-2.50wt.％;Cr：0.2-1.30wt.％;Mo：0.15-0.45wt.％;P：≤0.020wt.％;S：≤0.010wt.％;O：≤0.0015wt.％;N：≤0.0030wt.％; in parts by weight, and the balance of Fe and unavoidable impurities; The production method of the hot rolled wire rod for the ultra-high strength bridge cable sequentially comprises the steps of smelting, continuous casting, rolling, salt bath isothermal treatment, coil collecting and slow cooling treatment, continuous casting billets with the components and the proportion are obtained through the smelting and continuous casting steps, wires are spun at the temperature of 880-920 ℃ to be wire rods, the wire rods after spinning are directly immersed into a salt bath with the temperature of 200-300 ℃ to carry out isothermal treatment, medium-carbon martensite and non-transformed austenite are obtained, the wire rods after salt bath treatment are immediately collected and are subjected to slow cooling treatment in a constant-temperature annealing furnace with the temperature of 380-420 ℃ at the temperature of not lower than 180 ℃, carbon elements in the martensite are diffused into the non-transformed austenite, a small amount of bainite and residual austenite are obtained, and the wire rods finally obtain the composite microstructure of the low-carbon martensite, the small amount of bainite and the residual austenite.
  2. 2. The method for producing a hot rolled wire rod for ultra-high strength bridge cables according to claim 1, wherein the diameter of the wire rod is 7mm or 9mm, the tensile strength is 1700-1800MPa, and the area reduction is 48-58%.
  3. 3. The method for producing a hot rolled wire rod for ultra-high strength bridge cables according to claim 1, wherein the wire rod has a martensite ratio of 75-85%, a bainite ratio of 0-10%, and an austenite ratio of 10-15%.
  4. 4. The method for producing a hot rolled wire rod for ultra-high strength bridge cables according to claim 1, wherein the time of the salt bath isothermal treatment is 30-90S.
  5. 5. The method for producing a hot rolled wire rod for ultra-high strength bridge cable according to claim 1, wherein the time of the slow cooling treatment is not less than 30 minutes.
  6. 6. The method for producing a hot rolled wire rod for ultra-high strength bridge cables according to claim 1, wherein the continuous casting step is performed by rough rolling after heating the continuous casting billet, and then finish rolling, wherein the heating temperature is 1040-1150 ℃, the initial rolling temperature of rough rolling is 980-1020 ℃, and the inlet temperature of finish rolling is 880-920 ℃.
  7. 7. The method for producing a hot rolled wire rod for ultra-high strength bridge cables according to claim 1, wherein the continuous casting process obtains a rectangular billet having a cross-sectional dimension of not less than 240mm x 180mm to ensure a sufficient compression ratio after rolling into a wire rod to ensure homogeneity of the wire rod.
  8. 8. The method for producing a hot rolled wire rod for ultra-high strength bridge cables according to claim 1, wherein in the continuous casting process, the superheat degree of molten steel is controlled to be 30-45 ℃, the electromagnetic stirring current at the solidification end is 240+ -25A, the stirring frequency of a crystallizer is 5.5+ -0.5 Hz, the pulling rate during continuous casting is 1.05+ -0.05 m/min, and the specific water content of continuous casting is 0.30+ -0.01L/kg.

Description

Hot-rolled wire rod for ultra-high strength bridge cable and production method thereof Technical Field The invention relates to the technical field of metal wire manufacturing, in particular to a hot-rolled wire rod for an ultrahigh-strength bridge cable and a production method thereof. Background The galvanized steel wires of the bridge are used as core engineering materials for constructing large-span suspension bridges and cable-stayed bridges, and are always the important points for research and development of iron and steel enterprises and scientific research institutions. Based on the requirements on the rigidity, the service life and the safety of the whole bridge structure, the galvanized steel wires of the high-strength and ultra-high-strength bridges become the development direction, and the strength level of the ultra-high-strength bridge cable steel wires adopted in heavy point projects such as left alone without help ocean bridges, chang Tai bridges, nests Ma Daqiao and Zhang Jinggao bridges and the like constructed in recent years is continuously improved to 2060MPa, 2100MPa and 2200 MPa. The most critical index for researching and developing the hot dip galvanized steel wire for the ultra-high strength bridge cable is the torsion performance of the steel wire, the torsion performance of the galvanized or zinc-aluminum alloy steel wire is not lower than 8 times specified in national standard GB/T17101-2019 'hot dip galvanized zinc-aluminum alloy steel wire for bridge cable' issued in 2020, and the standard is further improved to more than 12 times in practical application. The existing manufacturing of bridge cable steel wires adopts high-carbon pearlite wire rods, and the processing technology comprises hot rolling of the wire rods, multi-pass drawing, hot galvanizing (aluminum), stabilization and finished steel wire production. The strength of the bridge cable wire is the wire rod initial strength + cold work hardening-strength loss of the galvanization (aluminum) treatment. The measures for improving the tensile strength are mainly to improve the carbon content of the wire rod to improve the tensile strength of the original wire rod, and to increase the diameter of the original wire rod to increase the deformation and the cold working strengthening. However, these measures bring about the reduction of the plasticity of the steel wire, so that the torsion frequency of another key performance index of the bridge cable steel wire cannot meet the requirement, and in fact, the biggest difficulty in manufacturing the existing ultra-high strength bridge cable steel wire is that the torsion index is difficult to meet while the strength is improved. A large number of researches show that the reasons for influencing the change of the torsion index of the bridge cable steel wire are mainly caused by the change of cementite phase in pearlite during the drawing and hot galvanizing processes. Cementite sheets in a pearlite structure gradually evolve into an amorphous structure due to large deformation in the wire rod drawing process, and at the moment, the cementite sheets have good deformation consistency with a ferrite phase which is severely deformed, so that the steel wire torsion index before galvanization is good. However, when the steel wire is subjected to subsequent hot dip galvanizing (aluminum), the amorphous cementite is converted into crystals again, and the torsion index of the finished galvanized (aluminum) steel wire is reduced sharply due to poor control. In order to inhibit the change, the current technical route adopted by the development of the bridge cable steel wire to high reinforcement is to greatly increase the carbon content in chemical components and add a large amount of Si, cr, V and other alloy elements, so that the production difficulty is increased, and the contradiction between the strength and torsion is more difficult to balance. Therefore, a brand new chemical composition and microstructure design are needed to solve the technical problem of poor torsion index of the ultra-high strength bridge cable steel wire. Disclosure of Invention The invention aims to provide a hot-rolled wire rod for an ultrahigh-strength bridge cable and a production method thereof, which are used for solving the problem that no segregation evaluation method for medium-low carbon steel (C < 0.4%) exists in the current industry. In order to achieve the above purpose, the present invention provides the following technical solutions: the hot rolled wire rod for the ultra-high strength bridge cable comprises the following chemical components ：C：0.24-0.36wt.％;Si：1.50-2.50wt.％;Mn：1.50-2.50wt.％;Cr：0.2-1.30wt.％;Mo：0.15-0.45wt.％;P：≤0.020wt.％;S：≤0.010wt.％;O：≤0.0015wt.％;N：≤0.0030wt.％; in parts by weight, and the balance of Fe and unavoidable impurities. Further, the diameter of the wire rod is 7mm or 9mm, the tensile strength is 1700-1800MPa, and the area reduction rate is 48-58%. Further, the wire rod com