CN-121976010-A - High-strength complex-phase hot-rolled wire rod for 2400 MPa-level stranded wire and manufacturing method thereof

CN121976010ACN 121976010 ACN121976010 ACN 121976010ACN-121976010-A

Abstract

The invention relates to a 2400 MPa-level high-strength complex-phase hot rolled wire rod and a manufacturing method thereof, which adopts a trace amount of high carbon components of Mo-Nb to design rolling spinning to form the wire rod, and then carries out on-line molten salt short quenching isothermal annealing treatment, so that the wire rod firstly passes through a front-stage molten salt treatment and enters a bainite phase region from an austenite state to promote the transformation of part of austenite to bainite, then passes through a rear-stage molten salt treatment, improves the molten salt temperature, promotes the decomposition and transformation of unconverted residual austenite to sorbite and carries out isothermal tempering, and finally carries out roller way slow cooling to prepare the hot rolled wire rod with a microstructure comprising tempered bainite and tempered sorbite and a complex-phase structure, thereby simplifying a component system, realizing the regulation and on-line annealing of the complex-phase structure, improving the matching of high-strength plastic and plasticity, reaching the tensile strength of 1588-1638 MPa and the section shrinkage of 30-36 percent, and promoting the efficient stable production of the wire rod so as to avoid the off-line heat treatment to manufacture the stranded wire.

Inventors

Peng Mengdu
HU JUNHUI
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. A manufacturing method of a high-strength complex-phase hot-rolled wire rod for 2400 MPa-level stranded wire is characterized by comprising the following steps: The method comprises the steps of rolling a hot rolled wire rod according to chemical components of the hot rolled wire rod, wherein the chemical components and the mass percent of the hot rolled wire rod comprise ：C：0.95％~0.98％、Si：0.73％~0.93％、Mn：0.75％~0.95％、Cr：0.46％~0.64％、Nb：0.030％~0.050％、Mo：0.10％~0.30％、P≤0.015％、S≤0.015％, and the balance of Fe and unavoidable impurities, the wire rod is spun into the wire rod according to the spinning temperature of more than or equal to 890 ℃, then the wire rod is subjected to online molten salt short quenching isothermal annealing treatment, 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 30 ℃ so as to enter a bainitic phase region from an austenitic state, the transformation of part of austenite into bainite is promoted, the temperature of the molten salt is further increased through the later-stage molten salt treatment, the decomposition of unconverted residual austenite is promoted to be transformed into sorbite, the isothermal tempering is carried out, and finally, the hot rolled wire rod with a microstructure comprising a complex phase structure consisting of tempered bainite and tempered sorbite is manufactured through roller way slow cooling.
2. The method for manufacturing a high-strength composite hot-rolled wire rod for 2400 MPa-level strands according to claim 1, wherein the soaking temperature of the heating furnace is controlled to be 1170-1220 ℃ and the furnace time is controlled to be 160-300 min before rolling.
3. The method for manufacturing a high-strength multi-phase hot rolled wire rod for 2400 MPa-level strands according to claim 1, wherein the initial rolling temperature is controlled to 1050 to 1100 ℃, the initial rolling reduction is controlled to 37 to 42%, the final rolling temperature is controlled to 900 to 940 ℃, and the final rolling reduction is controlled to 22 to 27%.
4. The method for producing a high-strength, multi-phase hot-rolled wire rod for 2400 MPa-grade stranded wire according to claim 1, wherein the wire laying temperature is controlled to 890 to 930 ℃ during the wire laying.
5. The method for manufacturing the high-strength multiphase hot rolled wire rod for 2400 MPa-level stranded wires, which is characterized in that the molten salt temperature of the front-stage molten salt treatment is 472-515 ℃, the treatment time is 5-24 s, the molten salt temperature of the rear-stage molten salt treatment is 532-572 ℃ and the treatment time is 200-350 s.
6. The manufacturing method of the high-strength multiphase hot rolled wire rod for 2400 MPa-level stranded wires, which is characterized in that the circulation amount of molten salt in the front-stage molten salt treatment is 500-600 t/h, the temperature of molten salt is Wen Sheng ℃ and the circulation amount of molten salt in the rear-stage molten salt treatment is 400-600 t/h, and the temperature of molten salt is less than or equal to 3 ℃.
7. The method for manufacturing a high-strength composite hot-rolled wire rod for 2400 MPa-level strands according to claim 5, wherein the roller way slow cooling control wire rod is cooled to below 280 ℃ at a slow cooling speed of 0.45-0.75 ℃ per second for coil collection.
8. A high-strength multi-phase hot-rolled wire rod for 2400 MPa-level stranded wire, characterized in that the hot-rolled wire rod is manufactured by the manufacturing method of 2400 MPa-level stranded wire according to any one of claims 1 to 7.
9. The 2400 MPa-level stranded wire high-strength multiphase hot rolled wire rod of claim 8, wherein the tempered bainite is 42% -54% by volume, the tempered sorbite is 46% -58% by volume, the lamellar spacing of the tempered sorbite is 75-120 nm, the mesh carbide level of the hot rolled wire rod is 0 level, and the same-circle difference of mechanical properties is less than or equal to 53MPa.
10. The high-strength multi-phase hot rolled wire rod for 2400 MPa-level strands according to claim 8, wherein the hot rolled wire rod has a diameter of 5.5 to 16mm, a tensile strength of 1588 to 1638MPa and a reduction of area of 30% to 36%.

Description

High-strength complex-phase hot-rolled wire rod for 2400 MPa-level 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 high-strength multiphase hot rolled wire rod for 2400 MPa-level stranded wires and a manufacturing method thereof. Background The prestress steel strand is used as a high-stress bearing tool, is widely applied to the fields of railway sleeper, expressway, bridge, overhead, urban overpass, building and the like, and can save materials, reduce cost and bring great convenience to construction due to the strength grade improvement of the prestress steel strand. The existing pearlite type hot rolled wire rod has excellent cold drawing performance, but because the structure strength is low, the strength can be greatly improved only by large cold drawing amount, after the strength grade is improved to 2000MPa, the strength grade is difficult to continuously improve only by cold drawing, and the structure state is regulated by off-line heat treatment, so that the production process and the cost of a user are increased, and therefore, the hot rolled wire rod for 2400 MPa-grade stranded wires and the manufacturing method thereof are required to be developed, and the off-line heat treatment is not needed, and the high-efficiency stable production can be realized. The existing high-carbon pearlite type hot rolled wire rod can be manufactured by adding a plurality of microalloy components and combining a stelmor air cooling line or a water cooling line or a salt bath process, but the manufacturing of the hot rolled wire rod for 2400 MPa-level stranded wires has the following technical bottlenecks: 1. In order to improve the strength of the wire rod and the sorbite rate, the content of components such as C, si, V and the like can be increased in the wire rod for the existing stranded wire, and the strong air cooling or water bath cooling treatment is combined after spinning, for example, the high carbon component design of the stress corrosion resistance ultra-high strength steel stranded wire rod and the manufacturing method of the steel stranded wire disclosed by the patent CN114369760B is adopted, and the sorbite structure wire rod is obtained by combining the online water bath cooling and water-out slow cooling process after spinning, on one hand, the wire rod is difficult to inhibit the formation of reticular carbide due to the high carbon component and the carbon segregation after spinning, the water bath cooling can improve the cooling speed of the wire rod, but a large amount of bubbles are formed to adhere to the surface of the wire rod to influence the heat transfer uniformity, the cold speed difference of different parts of the wire rod is influenced, the stable control of reticular carbide is influenced, the wire rod hardenability and the alloy element segregation influence, the local supercooling is easy to form martensite and other abnormal structures, and the temperature is high, the toughness performance and the structure uniformity of the wire rod are deteriorated, and the high temperature resistance is increased, the alloy is coarsened, the high-price alloy is greatly influenced, the high-limited alloy quality is formed, and the subsequent high-temperature alloy resistance is increased, and the final processing cost is increased; on the other hand, the phase change incubation period of sorbite is prolonged under the influence of high silicon and other components, the minimum cooling capacity is limited on a stelmor air cooling line or under the slow cooling of water outlet, the wire rod is in a low-temperature state after phase change incubation, abnormal tissues are difficult to toughen, the wire rod has larger residual stress, the final plastic toughness performance is insufficient and even brittleness is larger, the risk of wire breakage in subsequent processing is further increased, the hot rolled wire rod is difficult to stably produce or is free from off-line heat treatment. 2. In order to improve the strength and plasticity of the hot rolled wire rod for the stranded wire, although the prior art combines salt bath treatment, for example, 2400-2460 MPa-level stress corrosion resistant prestress wire rod for the stranded wire, steel stranded wire and production method disclosed by patent CN120400685A adopt C-Si-Mn-Cr-V-Nb component design to combine on-line salt bath isothermal treatment and slow cooling of not higher than 0.2 ℃ to manufacture sorbite structure wire rod, the sorbite bias sheet layer is limited in strengthening, V, nb multiple alloys are matched, the material cost and smelting difficulty are increased, the deformation resistance of a steel billet is greatly improved at low rolling temperature, the rolling efficiency is limited, meanwhile, the deformation resistance of the steel billet is limited by phase transition and one-section on-line salt bath isotherm