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CN-121976126-A - 2430 MPa-level hot-rolled wire rod for stranded wire and manufacturing method thereof

CN121976126ACN 121976126 ACN121976126 ACN 121976126ACN-121976126-A

Abstract

The invention relates to a hot rolled wire rod for 2430 MPa-level stranded wires and a manufacturing method thereof, wherein Al-Si-V chemical components are adopted to roll and spin into the wire rod, and then the wire rod is subjected to online molten salt rapid quenching isothermal treatment, so that the wire rod firstly passes through a front-stage molten salt treatment and rapidly cools, enters a sorbite phase region from an austenitic state to form a tissue mainly comprising sorbite tissues, then passes through a rear-stage molten salt treatment, reduces the circulation quantity of the molten salt, promotes the continuous conversion of unconverted residual austenite into sorbite and isothermal tempering, promotes the fusing of part of sorbite sheets, and finally passes through a roller way for slow cooling, so that the hot rolled wire rod with a microstructure comprising tempered sorbite, tempered ferrite and fused sorbite and a mixed tissue is manufactured, the material cost can be reduced, the abnormal tissue can be restrained, the tensile strength is 1581-1630 MPa, the section shrinkage rate is 34% -39%, and the efficient and stable production of ultra-high-strength stranded wires is promoted without offline heat treatment.

Inventors

  • Peng Mengdu
  • CHEN YUANQING
  • WANG MIAO
  • Rao Zicai
  • ZHANG YEFEI
  • SHI TONGTONG

Assignees

  • 江苏永钢集团有限公司
  • 联峰钢铁（张家港）有限公司

Dates

Publication Date
20260505
Application Date
20260407

Claims (10)

  1. 1. The manufacturing method of the hot-rolled wire rod for the 2430 MPa-level stranded wire is characterized by comprising the following steps of: The wire rod is rolled according to chemical components of a hot rolled wire rod, the chemical components and the mass percent of the hot rolled wire rod comprise ：C：0.93％~0.98％、Si：0.85％~1.05％、Mn：0.84％~1.01％、Cr：0.42％~0.62％、V：0.038％~0.044％、Al：0.25％~0.37％、P≤0.014％、S≤0.014％, balance Fe and unavoidable impurities, the wire rod is subjected to on-line molten salt rapid quenching isothermal treatment after being spun into the wire rod according to the spinning temperature of more than or equal to 895 ℃, the wire rod is firstly subjected to front-stage molten salt treatment and is cooled at the cooling speed of more than or equal to 33 ℃ per second, enters a sorbite phase region from an austenitic state to form a tissue mainly comprising sorbite tissue, is subjected to rear-stage molten salt treatment, reduces the circulation quantity of molten salt, promotes the unconverted residual austenite to be continuously converted into sorbite, is subjected to isothermal tempering, promotes part of sorbite sheet layers to fuse, and is finally subjected to roller way slow cooling to prepare the hot rolled wire rod with a mixed structure comprising tempered sorbite, tempered ferrite and fused sorbite.
  2. 2. The method for manufacturing a hot rolled wire rod for 2430 MPa-level stranded wire according to claim 1, wherein a soaking temperature of a heating furnace is controlled to be 1196-1246 ℃ before rolling, and a furnace time is 185-275 min.
  3. 3. The method for manufacturing a hot rolled wire rod for 2430 MPa-level stranded wire according to claim 1, wherein the initial rolling temperature is controlled to 1038-1088 ℃, the final rolling temperature is controlled to 905-945 ℃, and the final rolling reduction is controlled to 22-27%.
  4. 4. The method for producing a hot rolled wire rod for 2430MPa grade strands according to claim 1, wherein the spinning temperature is controlled to be 895 to 920 ℃.
  5. 5. The method for manufacturing a hot rolled wire rod for 2430 MPa-level stranded wire according to claim 1, wherein the molten salt temperature of the front-stage molten salt treatment is 558-588 ℃, the treatment time is 127-177 s, the molten salt temperature of the rear-stage molten salt treatment is 573-588 ℃, and the treatment time is 50-100 s.
  6. 6. The method for manufacturing the hot rolled wire rod for the 2430 MPa-level stranded wire, which is characterized in that the circulation amount of molten salt in the front-stage molten salt treatment is 480-680 t/h, the temperature rise of the molten salt is less than or equal to 8 ℃, the circulation amount of the molten salt in the rear-stage molten salt treatment is 300-425 t/h, and the temperature rise of the molten salt is less than or equal to 3 ℃.
  7. 7. The method for manufacturing a hot rolled wire rod for 2430 MPa-level stranded wires according to claim 5, wherein the roller way slow cooling control wire rod is cooled to 285 ℃ or below at a slow cooling rate of 0.35-0.65 ℃ per second for coiling.
  8. 8. A hot rolled wire rod for 2430 MPa-level stranded wire, characterized in that the hot rolled wire rod is produced by the method for producing a hot rolled wire rod for 2430 MPa-level stranded wire according to any one of claims 1 to 7.
  9. 9. The 2430 MPa-level hot-rolled wire rod for a stranded wire according to claim 8, wherein the volume percentage of tempered sorbite is equal to or more than 60%, the sheet spacing is 80-125 nm, the volume percentage of tempered ferrite is equal to or less than 6%, the volume percentage of fused sorbite is equal to or more than 24%, the mesh carbide grade of the hot-rolled wire rod is 0, and the same-circle difference of mechanical properties is equal to or less than 50MPa.
  10. 10. The hot rolled wire rod for 2430 MPa-level stranded wire according to claim 8, wherein the diameter of the hot rolled wire rod is 5.5-15 mm, the tensile strength is 1581-1630 MPa, and the reduction of area is 34-39%.

Description

2430 MPa-level hot-rolled wire rod for stranded wire and manufacturing method thereof Technical Field The invention belongs to the technical field of hot rolled wire rods, and particularly relates to a 2430 MPa-level hot rolled wire rod for stranded wires and a manufacturing method thereof. Background With the rapid development of the steel industry, the development of the ultra-high strength stranded wire is beneficial to meeting the reliability requirements of projects such as high-speed rail, offshore wind power and the like, the stranded wire is formed by taking a hot-rolled wire rod as a base material and processing the hot-rolled wire rod through working procedures such as drawing, twisting and the like, and the structure and mechanical properties of the hot-rolled wire rod are directly related to the drawability, strength level, fatigue life and engineering reliability of the stranded wire. The existing hot-rolled wire rod design for the ultra-high strength stranded wire generally improves the strength of the wire rod by adding 0.90% of carbon elements and other strengthening elements, but excessive carbon and other strengthening elements are extremely easy to generate abnormal structures such as high-grade net carbide, martensite and the like on the basis of the existing production line, so that cold-drawn broken wires appear in a downstream stranded wire plant, the cost is increased rapidly by adopting off-line heat treatment, and the development of the ultra-high strength stranded wire is limited, therefore, the 2430 MPa-grade hot-rolled wire rod for the stranded wire and the manufacturing method thereof need not be required to be subjected to off-line heat treatment, and the stable production of the ultra-high strength stranded wire can be promoted, so that the development of the steel industry and the use demands of markets are met. Although some wire rods for ultra-high strength stranded wires are proposed in the prior art, the following technical bottlenecks exist in manufacturing hot rolled wire rods for 2430 MPa-level stranded wires: 1. The prior wire rod for high-strength stranded wires is generally produced by combining with a stelmor air-cooled wire after spinning, the wire rod strength is increased, alloy components such as Si, mn, V, nb, ti are added in a high-carbon steel grade, a strong air-cooled process after spinning is matched to promote the refinement of a sheet layer into a sorbite structure, but on one hand, the high-carbon steel is high in C content and easy to generate segregation during continuous casting, the wire rod is limited by the highest cooling capacity of the stelmor air-cooled wire, austenite stays in a high temperature area for a long time, eutectoid cementite is easy to precipitate along the prior austenite grain boundary, and is continuous and net-formed, so that the net-shaped carbide severely breaks a matrix, influences the wire rod plastic toughness, and the influence of net-shaped carbide is reduced as much as possible, the influence of the air cooling strength is increased, the wire rod is further increased, the influence of the air-cooled surface is increased, the temperature difference between the wire rod edge part and the wire rod part is reduced, the quenching elements such as Mn, cr, B are combined, the like segregation influence of hardening elements such as martensite is increased, the like is caused by the fact that the wire rod brittleness and mechanical property fluctuation is easy to generate in a local supercooling area, the wire rod is not in coordination deformation during online cold drawing, the wire breakage is aggravated, and the wire rod is cut is promoted, while the prior art proposes that the cooling process such as CN 62 is long in a water bath, the wire rod is difficult to evenly, the wire rod is difficult to be cooled down, and the wire rod cooling structure is difficult to be uniform, and stable, the wire rod cooling strength is difficult to be controlled, and the wire rod cooling down, and has the wire rod cooling strength is difficult to be stable, and has the uniform, and stable, and the wire rod cooling structure is difficult to be stable, and has the wire rod cooling structure is difficult to be cooled down and has the wire rod, the fluctuation of mechanical properties is increased, too much noble microalloy material is added to lead to higher cost of the wire rod material, meanwhile, the wire rod is in a low-temperature state after phase change inoculation, and the tissue stress and the thermal stress in the phase change process are remained in the wire rod to further lead to insufficient plasticity of the wire rod and adverse subsequent drawing, so that the production bottleneck of off-line heat treatment free wire rod is difficult to break through. 2. In order to improve the strength and plasticity of stranded wire rods, salt bath treatment is proposed in the prior art, for example, 2400-2460 MPa-level stress corrosion resi