High-strength complex-phase hot-rolled wire rod for 2060MPa-grade stranded wire and manufacturing method of high-strength complex-phase hot-rolled wire rod

Abstract

The invention relates to a high-strength complex-phase hot-rolled wire rod for a 2060MPa-grade stranded wire and a manufacturing method of the high-strength complex-phase hot-rolled wire rod. After high-carbon chemical components containing trace V are designed, rolled and spun into a wire rod, the wire rod is cooled at a cooling speed of more than or equal to 33 DEG C / s through on-line molten salt semi-quenching treatment, enters a bainite and pearlite mixed phase region from an austenite state, and is subjected to hot rolling and hot rolling at a cooling speed of more than or equal to 33 DEG C / s; the method comprises the following steps: quenching bainite and a sorbite structure to form a structure mainly comprising the quenched bainite and the sorbite structure, then carrying out isothermal tempering, and finally carrying out roller way slow cooling to prepare the hot-rolled wire rod of which the microscopic structure comprises a complex-phase structure consisting of tempered sorbite and tempered bainite, so that a component system can be simplified, the material cost can be reduced, network carbides can be effectively controlled, and meanwhile, the complex-phase structure can be regulated and controlled; the high strength and plasticity of the wire rod are matched, the tensile strength is 1390-1440 MPa, the percentage reduction of area is 32%-37%, and the steel wire rod is used for manufacturing 2060 MPa grade stranded wires and other application fields and is beneficial to downstream wire drawing and twisting processing.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hot-rolled wire rod, and particularly relates to a 2060MPa-grade high-strength multiphase hot-rolled wire rod for stranded wire and a manufacturing method thereof. BACKGROUND

[0002] The strength grade of steel strand is improved, which can effectively promote large engineering projects to develop in a higher stress service environment, and also can promote the decrease of the use of high-strength stranded wire, so as to achieve the purpose of energy saving and consumption reduction. The steel strand takes the hot-rolled wire rod as the base material, removes the surface defects through pretreatment, is drawn into steel wire through multiple passes, and is twisted and formed into a strand, so the quality of the hot-rolled wire rod is directly related to the performance and stable production of the steel strand. At present, the pearlite type steel strand as the main steel grade becomes the mainstream in the field of steel strand, and the steel strands of other organizational types are less developed, because the hot-rolled wire rod for steel strand is usually produced through a Stelmor air cooling line. For example, a 1960-2060MPa-grade prestressed steel strand and a preparation method thereof disclosed in patent CN117845141A adopt a high-carbon component design of C-Mn-Si-Cr-V-Ti-Nb to combine with low-speed air cooling to prepare a pearlite organizational wire rod, but the following technical defects still exist: I. In order to refine the pearlite lamellar spacing and improve the mechanical strength of the alloy, the wire rod adopts a high-carbon composition system of multi-element alloy strengthening, Cr is added as an alloying element on the basis of Mn-Si main alloying, but it also increases the material cost and smelting difficulty, and the high Si increases the work hardening sensitivity, leading to the concentration of plastic deformation, and there is certain segregation in the alloy composition during solidification. Cr is easy to segregate to the austenite grain boundary at high temperature, reducing the grain boundary bonding force and exacerbating the grain boundary embrittlement. With the increase of the air cooling intensity, the risk of martensite and other abnormal organizations precipitating will be further increased, leading to the increase of the mechanical property fluctuation of the wire rod, causing the risk of brittle fracture in the subsequent process. In order to reduce the material cost, smelting difficulty and processing sensitivity, the alloy content is reduced and the composition system is simplified. On the one hand, the sorbite phase transformation starting temperature is increased, and the promotion effect of Cr on the nucleation and growth of carbide is lacking, which needs to be combined with low-temperature controlled rolling and rapid cooling. However, low-temperature controlled rolling will affect the rolling production efficiency and increase the load demand of the rolling line. At the same time, limited by the maximum cooling capacity of the Stelmor air cooling line, the wire rod slowly passes through the temperature range of secondary cementite and pearlite precipitation. During the wire drawing and air cooling process, high-carbon enrichment is easy to form network carbide, which will cut the continuity of the pearlite matrix, affect the plasticity and toughness of the wire rod, and lead to uneven deformation transmission in the subsequent wire drawing or twisting process, becoming the crack initiation source. On the other hand, the hardenability of the wire rod is reduced. With the increase of the air cooling intensity of the Stelmor air cooling line, the cooling speed difference between the core and the surface of the wire rod is further enlarged due to the unstable controlled temperature. Especially with the decrease of the diameter specification of the wire rod, the surface or local cooling is easy to form low-temperature brittle structure, and the core cooling is easy to cause the coarsening of cementite in the cooling process. With the carbon segregation in the core, the unevenness of the pearlite is further intensified, resulting in a large strength loss and mechanical property fluctuation, leading to the difficulty in achieving the target strength and the large anisotropy, which is not conducive to the downstream wire drawing.

[0003] II. In order to improve the drawing performance, V, Ti, Nb and other strong carbide forming elements are added to the wire rod to refine the grain, but limited by the minimum cooling capacity and continuous cooling of the Stelmor air cooling line, the precipitation driving force is insufficient, which is easy to lead to the insufficient and uneven precipitation of micro-alloy carbide, making it difficult to fully play its strengthening role. As a result, the required content and elements are more, which will bring the increase of the material cost as a precious alloy element. After reducing the micro-alloy content and simplifying the composition system, the austenite grain becomes coarse, the nucleation efficiency is reduced, and limited by the maximum cooling capacity of the air cooling, the organization is easy to be coarsened, resulting in a significant strength loss, which is not conducive to the development of the steel strand to the super-high strengthening direction. SUMMARY

[0004] The application aims to solve at least one of the above technical problems, and provides a high-strength complex-phase hot-rolled wire rod for 2060MPa-grade stranded wires and a manufacturing method thereof, which can simplify the component system, reduce the material cost, effectively control the network carbide, and realize complex-phase structure regulation and control, thereby improving the high-strength and plasticity matching of the wire rod and being beneficial to downstream drawing and twisting processing.

[0005] The application adopts the technical scheme for solving the technical problems: The manufacturing method of the high-strength complex-phase hot-rolled wire rod for 2060MPa-grade stranded wires comprises the following steps: The wire rod is produced by rolling according to the chemical composition of the hot-rolled wire rod, and the chemical composition and mass percentage of the hot-rolled wire rod comprises: C: 0.84% to 0.88%, Si: 0.30% to 0.47%, Mn: 0.65% to 0.85%, V: 0.01% to 0.03%, P≤0.015%, S≤0.015%, and the rest is Fe and inevitable impurities; after the wire rod is produced by wire drawing according to a wire drawing temperature of ≥880℃, the wire rod is subjected to on-line molten salt semi-quenching treatment, so that the wire rod is cooled at a cooling rate of ≥33℃ / s from an austenite state into a mixed phase region of bainite and pearlite, a structure mainly composed of quenched bainite and sorbite is formed, and then isothermal tempering is performed, and finally the wire rod is prepared by roller slow cooling, and the hot-rolled wire rod with complex-phase microstructure composed of tempered sorbite and quenched bainite is obtained.

[0006] The design basis of the chemical composition and mass percentage of the hot-rolled wire rod comprises: (1) Carbon: C is a solid solution strengthening element in steel, and the price is relatively lower. C forms an interstitial solid solution in the iron matrix and forms carbides with V, can hinder dislocation movement, improve the strength of the matrix, can reduce the pearlite transformation temperature during on-line molten salt semi-quenching, expand the austenite stable region and bainite transformation region, delay the transformation of austenite to pearlite, and promote a small amount of quenched bainite transformation. However, if the content of C is too high, the center segregation of high-carbon steel billets, the control of network carbide and carbide coarsening will be difficult, the enrichment of carbon in austenite will increase the proportion of bainite in the complex-phase structure, there is a risk of martensite precipitation, and the toughness and drawing plasticity will be affected. Therefore, in order to meet the high-strength requirement of 2060MPa-grade stranded wires, reduce the control difficulty of structure uniformity and abnormal structure, and adapt to complex-phase structure regulation and control, the mass percentage of C is controlled to be 0.84% to 0.88%.

[0007] (2) Silicon: Si element can be dissolved in the iron matrix by solid solution strengthening to cause lattice distortion, hinder dislocation movement, and improve the hardness and strength of the matrix. During the online molten salt semi-quenching process, silicon can be enriched at the austenite or cementite interface to hinder the diffusion of carbon atoms to cementite, delay the pearlite transformation kinetics, and help promote the bainite transformation. Meanwhile, it can delay the transformation of carbides from a fine dispersed state to a coarse aggregated state, so that the strength after tempering can still be relatively high. However, excessive silicon can promote decarburization and prolong the phase transformation incubation period. The degree of lattice distortion and the resistance to dislocation movement will increase the difficulty of softening, leading to a decrease in the plasticity and production efficiency of the steel, and then causing fracture during subsequent drawing and twisting processes, affecting the yield of the stranded wire. Therefore, in order to adapt to the regulation of the phase transformation structure by online molten salt semi-quenching, the mass percentage of Si is controlled to be 0.30% to 0.47%.

[0008] (3) Manganese: Mn is a strong austenite stabilizing element. During the online molten salt semi-quenching process, it can lower the transformation temperature of austenite to pearlite or bainite. The decrease in the transformation temperature will make the transformation products of sorbite and bainite finer, avoiding the coarsening of pearlite or the premature precipitation of ferrite. Through lattice distortion to hinder dislocation movement, it forms a synergistic effect with Si solid solution strengthening to improve the matrix strength. However, excessive Mn will increase element segregation during the solidification of the billet, increase the high-temperature strength of the steel, and require greater rolling force during rolling, which can easily lead to increased wear of the rolls and rolling load exceeding the limit. Mn is prone to segregate at the austenite grain boundaries at high temperatures, and low-temperature martensite structure is easily formed during the cooling process, increasing the risk of abnormal structure precipitation and stress concentration, and thus increasing the risk of brittle fracture during subsequent drawing and twisting. It also increases the difficulty of tempering softening, and thus reduces the plasticity of the wire rod. Therefore, in order to balance the regulation of the complex phase structure of the hot-rolled wire rod and reduce the difficulty of tempering control, the mass percentage of Mn is controlled to be 0.65% to 0.85%.

[0009] (4) Vanadium: As a micro-alloying element, V can be strain-induced precipitated during high-temperature hot rolling, pinning grain boundaries to refine grains and increase the nucleation core of sorbite transformation, which is helpful to obtain fine and uniform sorbite structure and beneficial to the formation of bainite at a lower temperature, making the bainite structure more fine and dispersed. Excessive V can be dispersedly precipitated as nanoscale VC precipitates during isothermal process at medium temperature, rapidly strengthening the matrix through solid solution strengthening and precipitation strengthening. However, the price of V is relatively high, and excessive addition is not conducive to controlling the cost of the material. Therefore, the mass percentage of V is controlled to be 0.01% to 0.03%.

[0010] (5) Phosphorus and sulfur: P and S elements are impurity elements, and the lower the better. Therefore, P is controlled to be ≤0.015%, and S is controlled to be ≤0.015%.

[0011] The hot-rolled wire rod adopts a high-carbon composition design of C-Si-Mn-V, does not contain elements such as Cr, Nb, Ti, and V is added in a trace amount, which can simplify the composition system, reduce the material cost, and optimize the proportioning of each element, regulate the hardenability of the wire rod, expand the bainite phase transformation interval, provide favorable conditions for forming a bainite and pearlite mixed phase zone, reducing the risk of composition segregation, inhibiting the coarsening of pearlite and ferrite, promoting the synchronous phase transformation of a small amount of bainite and a large amount of sorbite, and facilitating the regulation of the complex phase structure and the uniformity of the structure. On this basis, a relatively high wire laying temperature is selected to make the wire rod austenitize completely and avoid the formation of network carbide at the wire laying stage due to a too low temperature, and a temperature difference is formed with the molten salt temperature to provide favorable conditions for obtaining sufficient supercooling degree and promoting the synchronous phase transformation of bainite and sorbite. The wire rod is not air-cooled after wire laying but is subjected to on-line molten salt semi-quenching treatment: I. Compared with the simplified composition system, it is difficult to inhibit network carbide and regulate the complex phase structure due to the limitation of the highest cooling capacity and unstable temperature control of the Stelmor air-cooling line. On the one hand, the rapid cooling capacity of the molten salt can be utilized to promote the rapid cooling of the wire rod from the high-temperature austenite state, bypass the precipitation temperature interval of secondary cementite, inhibit the network carbide caused by high carbon, increase the supercooling degree and phase transformation driving force by utilizing rapid cooling, avoid the early precipitation of pearlite and ferrite soft phase in the initial cooling stage to cause strength loss and mechanical property fluctuation, expand the bainite phase zone, and promote the synchronous phase transformation of a small amount of bainite, promote the refinement of cementite lamella to form a large amount of sorbite structure with finer lamellar spacing, and improve the nucleation rate to compensate for the adverse effects of the omission of alloying elements and the coarsening of cementite on the phase transformation driving force and improve the matrix strength. On the other hand, when the wire rod passes through the molten salt, the molten salt can cover the surface of the wire rod for uniform heat exchange, making the bainite phase transformation, which is usually considered as an abnormal structure, controllable. Meanwhile, the bainite and pearlite mixed phase zone has a higher temperature than the martensite phase zone, especially as the diameter specification of the wire rod decreases, the formation of martensite brittle structure due to local supercooling under the influence of segregation can be avoided, and as the treatment time is prolonged, the temperature gradient from the surface to the core of the wire rod can be further reduced to promote the full transformation of the structure and avoid the continuous formation of martensite structure in the subsequent cooling process due to the austenite residue, thereby improving the uniformity of the structure and reducing the risk of brittleness.

[0012] Secondly, compared with the minimum cooling capacity and continuous cooling limitation of Stelmor air cooling line, the VC precipitation power can be improved under rapid cooling to avoid coarse precipitation of VC after long time at high temperature, avoid uneven precipitation of VC, and with the extension of treatment time, the excess V can be fully dispersed and precipitated as nanoscale VC precipitates in the online molten salt semi-quenching process at medium temperature, so as to fully play the dispersion strengthening effect, make up for the strength loss in isothermal tempering, and provide good cold drawing performance; on the other hand, in the online molten salt semi-quenching process, the temperature of the rod gradually changes to the isothermal treatment temperature consistent with the molten salt temperature, rather than continuous cooling, and after phase transition, the rod can stay in the medium temperature range for a long time rather than in a low temperature state, the carbon diffusion capacity is enhanced, the metastable carbide can be converted to stable cementite, thereby reducing the dislocation density of bainite, refining and stabilizing the carbide, eliminating the internal stress of quenching, effectively improving the bainite brittleness and stress concentration, and finally slow cooling on the roller to prolong the slow cooling of the rod after leaving the molten salt, promote the further toughening of the structure, and thus regulate the complex phase structure and tempering state, effectively improve the overall strength and plasticity matching of the rod on the basis of simplifying the composition.

[0013] Before rolling, the soaking temperature and soaking time in the furnace can be controlled to make the surface and internal temperature of the billet consistent, reduce segregation, improve rolling plasticity, reduce deformation resistance, provide a good organizational basis for subsequent rolling, and avoid overheating caused by too high soaking temperature and too long soaking time in the furnace. In the preferred technical solution, before rolling, the soaking temperature in the furnace is controlled to be 1170-1210°C, and the soaking time in the furnace is controlled to be 160-250 min.

[0014] Due to the high spinning temperature, the limitation on rolling temperature can be reduced, and a higher initial rolling temperature can be used to reduce the wear of the rolling line and improve the rolling speed. The final rolling temperature and the final rolling reduction are controlled to strain induce precipitation of V to pin grain boundaries and refine grains, and to provide favorable conditions for the formation of refined structure during subsequent cooling. In the preferred technical solution, during rolling, the initial rolling temperature is controlled to be 1065-1100°C, the final rolling temperature is controlled to be 890-930°C, and the final rolling reduction is controlled to be 27%-32%.

[0015] During spinning, the spinning temperature can be further controlled to inhibit the growth of austenite grains. In the preferred technical solution, during spinning, the spinning temperature is controlled to be 880-915°C.

[0016] In the preferred technical solution, the online molten salt semi-quenching process is divided into a front-stage molten salt treatment and a rear-stage molten salt treatment, and the molten salt circulation amount of the front-stage molten salt treatment is greater than that of the rear-stage molten salt treatment. With the extension of the treatment time, the temperature difference between the surface and the core of the rod gradually decreases, and the appropriate reduction of the molten salt circulation amount in the rear-stage molten salt treatment can further reduce the production energy consumption and cost.

[0017] The molten salt temperature of the preceding molten salt treatment is in the mixed phase region of bainite and pearlite, and the lower the molten salt temperature is, the more conducive to inhibiting the formation of network carbide, while increasing the undercooling degree, inhibiting the premature precipitation of coarse pearlite and ferrite, promoting the preferential nucleation of bainite at the austenite grain boundaries and dislocations, and promoting the reduction of the interlamellar spacing of sorbite, and with the extension of the treatment time, the diffusion precipitation driving force of vanadium-containing carbide can be increased, and nano-scale precipitates can be simultaneously precipitated during the bainite and sorbite transformation, thereby improving the strength of the matrix; however, if the molten salt temperature is too low and the treatment time is too long, the bainite in the transformation product will increase, the sorbite transformation will be affected, the dislocation density and stress of the structure will be large, the softening difficulty and production energy consumption will be increased, and the plasticity and production efficiency of the structure will be affected; on the contrary, the higher the molten salt temperature is and the shorter the treatment time is, the more conducive to reducing the precipitation risk of abnormal structures such as martensite, promoting the sorbite transformation, reducing the stress and thermal stress of the structure, reducing the difficulty of stress release, reducing the production energy consumption, and promoting rapid production, but if the molten salt temperature is too high and the treatment time is too short, it is not conducive to inhibiting network carbide and abnormal structures, the driving force of bainite and vanadium-containing carbide formation will decrease, and the strength and uniformity of the matrix will decrease; therefore, the molten salt temperature and treatment time of the preceding treatment can be controlled to make the wire rod quickly enter the mixed phase region of bainite and pearlite from the high-temperature austenite state, form a structure mainly composed of quenched bainite and fine interlamellar spacing sorbite structure, promote the precipitation of nano-scale precipitates, take into account the production energy consumption, and prepare for the subsequent molten salt treatment in terms of structure, and in the preferred technical solution, the molten salt temperature of the preceding molten salt treatment is 455-485℃, and the treatment time is 45-150s.

[0018] Because the spinning temperature is greatly different from the molten salt temperature of the preceding molten salt treatment, a large molten salt circulation amount can be selected to reduce the molten salt temperature rise and improve the uniformity of the wire rod structure during continuous treatment, and in the preferred technical solution, the molten salt circulation amount of the preceding molten salt treatment is 450-650t / h, and the molten salt temperature rise is ≤10℃.

[0019] The molten salt temperature of the latter stage molten salt treatment is in the mixed phase region of bainite and pearlite, the higher the molten salt temperature and the longer the treatment time, the more conducive to improving atomic diffusion capacity, reducing the dislocation density of quenched bainite, promoting the release of organizational stress, promoting the full dispersion of vanadium-containing carbides, and improving the overall plasticity and toughness, but if the molten salt temperature is too high and the treatment time is too long, the atomic diffusion capacity is enhanced, the structure is excessively tempered and softened, which will cause strength loss, and the VC is easy to coarsen, which will cause plasticity loss and increase production energy consumption; on the contrary, the lower the molten salt temperature and the shorter the treatment time, the more conducive to reducing the softening speed and production energy consumption, shortening the production time, inhibiting the coarsening of the dispersed phase, and reducing the strength loss, but if the molten salt temperature is too low and the treatment time is too short, it is not conducive to isothermal tempering softening, vanadium-containing carbides cannot be fully precipitated, and the organizational stress cannot be fully released, which will cause plasticity loss; therefore, the molten salt temperature and the treatment time of the latter stage can be further controlled to promote the isothermal tempering of the quenched bainite and sorbite structure formed, control the dispersion of carbides, and adjust the strength and plasticity matching of the wire rod; in the preferred technical solution, the molten salt temperature of the latter stage molten salt treatment is 450-470℃, and the treatment time is 210-400s.

[0020] Since the molten salt temperature of the former stage molten salt treatment and the latter stage molten salt treatment is relatively small, the latter stage molten salt treatment can appropriately reduce the molten salt circulation amount, control the molten salt temperature rise, and reduce production energy consumption; in the preferred technical solution, the molten salt circulation amount of the latter stage molten salt treatment is 200-310t / h, and the molten salt temperature rise is ≤3℃.

[0021] The roller slow cooling can further control the slow cooling speed of the wire rod, avoid insufficient plasticity of the wire rod due to insufficient slow cooling, and promote the further toughening of the wire rod structure and improve the tempering softening effect of the wire rod; in the preferred technical solution, the roller slow cooling controls the wire rod to be cooled to below 280℃ at a slow cooling speed of ≤0.5℃ / s for coiling.

[0022] In the preferred technical solution, the roller slow cooling controls the opening of the heat preservation cover, blows hot air ≥250℃ to the conveying roller during online molten salt semi-quenching treatment, and controls the slow cooling of the wire rod through the heat preservation cover after the wire rod is conveyed by the conveying roller, which can further recover and utilize the heat energy of the online molten salt semi-quenching, reduce production energy consumption, and promote the rapid offline of the wire rod.

[0023] A 2060MPa grade high-strength complex phase hot-rolled wire rod for stranded wire, which is manufactured by the manufacturing method of the 2060MPa grade high-strength complex phase hot-rolled wire rod for stranded wire described in any one of the above.

[0024] The high-carbon carbon chemical composition design containing trace V can reduce material cost and smelting difficulty, and the microstructure includes complex phase structure composed of tempered sorbite and tempered bainite, can effectively inhibit abnormal structures such as reticular carbide and martensite compared with traditional high-strength twisted wire steel high-carbon steel pearlite rod, the lamellar spacing of sorbite is finer than that of pearlite, and higher strength and toughness are obtained, after stress release by tempering, the intermediate transition state tempered sorbite transformed from spheroidization structure can further improve plasticity and toughness, is suitable for multi-pass drawing, the bainite contains distortion and high-density dislocation, has higher strength, after tempering to reduce dislocation to be transformed into tempered bainite, the strength characteristics can be reserved, combined with the dispersion precipitation of VC nanoscale alloy carbide, the pinning dislocation ability is stronger, the strengthening effect of carbon and vanadium is fully played, the strength loss caused by the simplified composition system is compensated, meanwhile, the brittleness of bainite which is conventionally regarded as abnormal structure is effectively improved, the overall plasticity and strength matching is improved, the microstructure uniformity is improved, and the cold work hardening rate is more gentle, so that the risk of wire breakage in subsequent drawing and twisting processes is reduced.

[0025] In the microstructure, the higher the volume percentage of the tempered sorbite and the finer the lamellar spacing, the better the plasticity and toughness, and the higher the volume percentage of the tempered bainite, the higher the matrix strength, in the preferred technical solution, the volume percentage of the tempered sorbite is 65% to 75%, the lamellar spacing is 65 to 110 nm, and the volume percentage of the tempered bainite is 25% to 35%.

[0026] In the preferred technical solution, the reticular carbide level of the hot-rolled rod is 0, the mechanical property difference between turns is less than or equal to 40 MPa, the deterioration of the toughness of the rod caused by the reticular carbide can be effectively prevented, the rod is prevented from being broken due to the fact that the carbide cuts the matrix during processing or service, meanwhile, the abnormal structures such as coarse pearlite and martensite are avoided to be precipitated, the stress of the structure is released, the microstructure uniformity is improved, the fluctuation of the mechanical property is reduced, the overall deformation resistance of the rod is uniform, the tension fluctuation is small during the drawing process, and the stability during the twisting processing and service is improved.

[0027] In the preferred technical solution, the diameter of the hot-rolled rod is 5.0 to 14.0 mm, the tensile strength is 1390 to 1440 MPa, and the reduction of area is 32% to 37%, the diameter of the hot-rolled rod is small, the tensile strength is large, the drawing pass is reduced, the target diameter and strength of the twisted wire are quickly reached, the production efficiency is improved, the plasticity loss in the drawing process is reduced, the twisted wire is suitable for applications in multiple fields, the reduction of area is high, the hot-rolled rod can keep stable in shape and size during the processing and transportation, the plasticity demand of the cold drawing large deformation is met, the risk of wire breakage during drawing is prevented, the toughness is ensured for the service of the twisted wire, and the risk of brittle fracture is avoided.

[0028] Compared with the prior art, the present application has at least the following beneficial effects: (1) In view of the fact that the hot rolled wire rod for steel strand is usually produced by Stelmor air cooling line, resulting in complex material composition, existence of martensite and other organizations, and extremely brittle state, the present application controls the wire rod after wire drawing from high temperature austenite state into bainite and pearlite mixed phase zone by V-containing chemical composition design combined with on-line molten salt semi-quenching technology, suppresses reticular carbide and coarse pearlite, forms a complex phase mainly composed of quenched bainite and fine interlamellar spacing sorbite organization, avoids the formation of martensite organization, and improves brittleness through isothermal tempering toughening effect, promotes the dispersion precipitation of vanadium-containing carbide, and finally the roller slow cooling further improves the wire rod tempering softening effect, realizes the regulation of complex phase organization, improves the high strength and plasticity matching of the wire rod, and has good industrial adaptability.

[0029] (2) In view of the fact that the hot rolled wire rod material of pearlite type steel strand is high in cost and is not conducive to downstream wire drawing, the present application has a high-carbon carbon chemical composition design containing trace V, which can simplify the composition system, reduce the material cost, effectively control the reticular carbide, and the microstructure includes complex phase composed of tempered sorbite and tempered bainite, so that the bainite brittleness which is conventionally regarded as abnormal organization is effectively improved, the strength loss caused by the simplified composition system is compensated, the strength and plasticity matching of the wire rod is regulated, the tensile strength can reach 1390-1440 MPa, the reduction of area is 32%-37%, and the wire rod is used for manufacturing 2060 MPa grade strand and other application fields, which is conducive to downstream wire drawing and twisting processing, and has good market application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0030] The above and / or additional aspects and advantages of the present application will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the following drawings of which: Figure 1 is the metallographic structure diagram of example 1 of the present application; Figure 2 is the metallographic structure diagram of example 2 of the present application; Figure 3 is the metallographic structure diagram of example 3 of the present application. DETAILED DESCRIPTION

[0031] The embodiments described below with reference to the drawings are exemplary, are merely for illustration and do not limit the description of the features and characteristics of the present application, are intended to propose the best mode of carrying out the present application, are intended to serve for explaining the present application, and are sufficient to enable a person skilled in the art to implement the present application, and cannot be understood as any limitation on the scope of the present application, the scope of the present application is limited only by the appended claims; the structure and performance detection of the hot-rolled wire rod obtained in the following examples and comparative examples includes: the tensile test is tested according to GB-T228.1-2021 Metal Materials Tensile Test Part 1: Room Temperature Test Method to obtain the tensile strength and the area reduction rate; the structure detection is performed according to the metal microstructure detection method of GB / T13298 standard; the mechanical property same circle difference test method: 2 circles of wire rod are taken at a distance of 5m from the end of the coil, the lap joint area position is taken as the base point, each circle of wire rod is equally divided into 8 segments, and 1 tensile sample is taken on each segment, and the strength range of the tensile sample after the tensile test is the mechanical property same circle difference. Example 1

[0032] In a preferred embodiment of the manufacturing method of the 2060MPa-grade high-strength composite hot-rolled wire rod for stranded wire, the chemical composition and mass percentage of the hot-rolled wire rod include C: 0.88%, Si: 0.39%, Mn: 0.65%, V: 0.01%, P: 0.013%, S: 0.013%, and the rest is Fe and unavoidable impurities; the manufacturing method is manufactured according to the process flow of rolling→ wire drawing→ on-line molten salt semi-quenching→ roller slow cooling→ coil collecting, specifically: The rolling process is used to heat the steel billet with a specification of 180mm*180mm to a high-temperature steel billet with a rolling plasticity by a heating furnace, reduce composition segregation and avoid overburning, and the steel billet is rolled into a wire rod with a diameter specification of 5mm after the steel billet is discharged from the heating furnace through a rolling line, appropriate rolling temperature and reduction are selected, strain-induced precipitation V pins grain boundary to refine grains, specifically: the soaking temperature of the heating furnace is controlled to be 1170℃, the furnace time is 250min, the initial rolling temperature is 1065℃, the final rolling temperature is 890℃, and the final rolling reduction is 32%; the wire drawing process is used to draw the wire rod discharged from the rolling line through a wire drawing machine to form a wire rod, the wire rod is scattered on a roller and conveyed along the roller, appropriate wire drawing temperature is selected, the wire rod is in a high-temperature austenitizing state, and the wire drawing stage is avoided to precipitate net-shaped carbide, which provides favorable conditions for promoting the synchronous phase change of bainite and sorbite, specifically: the wire drawing temperature is controlled to be 880℃.

[0033] The online molten salt semi-quenching process adopts two-stage salt bath tanks with molten salt inside. The wire rod after wire drawing is conveyed through the first-stage salt bath tank for front-stage molten salt treatment, so that the wire rod is cooled at a cooling rate of 33℃ / s, quickly passes through the interlaced carbide zone from the high-temperature austenite state into the mixed phase zone of bainite and pearlite, inhibits the formation of interlaced carbide and coarse pearlite, forms the microstructure mainly composed of a small part of quenched bainite and a large part of fine lamellar interlaced sorbite, promotes the dispersion of vanadium-containing carbide, and then the wire rod is conveyed through the second-stage salt bath tank for rear-stage molten salt treatment, reduces the molten salt circulation amount, promotes the isothermal tempering of the quenched bainite and sorbite microstructure formed, avoids the coarsening of carbide, and adjusts the strength and plasticity matching of the wire rod. Specifically, the molten salt temperature of the front-stage molten salt treatment is 483℃, the treatment time is 45s, the molten salt circulation amount is 450t / h, and the molten salt temperature rise is ≤10℃; the molten salt temperature of the rear-stage molten salt treatment is 450℃, the treatment time is 400s, the molten salt circulation amount is 200t / h, and the molten salt temperature rise is ≤3℃.

[0034] The roller slow cooling process blows hot air ≥250℃ above the two-stage salt bath tanks of the online molten salt semi-quenching treatment to the conveying roller through controlling the opening degree of the heat preservation cover, conveys the wire rod through the heat preservation cover through the conveying roller, promotes the further toughening of the wire rod microstructure, and improves the tempering softening effect of the wire rod. Specifically, the wire rod is cooled to 278℃ at a slow cooling rate of 0.25℃ / s. Figure 1 The coiling process is used to coil the wire rod into a coil through a coiling drum, and the hot-rolled wire rod product is obtained after packaging and storage, and the metallographic structure diagram is as shown in

[0035] Comparative Example 1 A manufacturing method of a hot-rolled wire rod, which is different from the manufacturing method of Example 1 in that the manufacturing method is manufactured according to the process flow of rolling→wire drawing→Stelmor forced air cooling. Specifically, the heating furnace soaking temperature is controlled to be 1150℃, the furnace time is 265min, the rough rolling temperature is 1040℃, the finish rolling temperature is 825℃, and the wire drawing temperature is 810℃; the Stelmor forced air cooling adopts a wind volume of 260,000m 3 / h per fan, 1~4# fans are opened at 65%, the wire rod is cooled to 695℃ at a cooling rate of 5.8℃ / s, 5~14# fans are opened at 35%, the wire rod is cooled to 270℃ at a cooling rate of 3.2℃ / s, and the hot-rolled wire rod product is obtained after offline.

[0036] Comparative Example 2 A manufacturing method of hot-rolled wire rod, the manufacturing method is different from that of embodiment 1 in that: the soaking temperature of the heating furnace is controlled to be 1150 DEG C, the furnace time is 265 min, the rough rolling temperature is 1040 DEG C, the finish rolling temperature is 850 DEG C, the wire drawing temperature is 825 DEG C, and the wire rod is cooled at a cooling rate of 30 DEG C / s before the online molten salt semi-quenching process, and the hot-rolled wire rod product is obtained after being taken offline. Embodiment 2

[0037] A preferred embodiment of the manufacturing method of the 2060 MPa high-strength composite hot-rolled wire rod for stranded wire, the chemical composition and mass percentage of the hot-rolled wire rod include C: 0.85%, Si: 0.30%, Mn: 0.77%, V: 0.017%, P: 0.015%, S: 0.013%, and the rest is Fe and inevitable impurities; the manufacturing method is manufactured according to the process flow of rolling→wire drawing→online molten salt semi-quenching→roller slow cooling→coiling, specifically: The rolling process is used to heat the steel billet with a size of 180 mm*180 mm to a high-temperature steel billet with rolling plasticity through a heating furnace, reduce composition segregation and avoid overburning, and the steel billet is rolled into a wire rod with a diameter size of 8 mm after the steel billet is taken out of the heating furnace through a rolling line, and appropriate rolling temperature and reduction are selected, strain-induced precipitation V pinning grain boundary refines grains, specifically: the soaking temperature of the heating furnace is controlled to be 1185 DEG C, the furnace time is 215 min, the rough rolling temperature is 1085 DEG C, the finish rolling temperature is 905 DEG C, and the finish rolling reduction is 30%; the wire drawing process is used to make the wire rod out of the rolling line into a wire rod through a wire drawing machine, the wire rod is scattered on the roller way and conveyed along the roller way, appropriate wire drawing temperature is selected, the wire rod is in a high-temperature austenitizing state, and the precipitation of net-shaped carbide at the wire drawing stage is avoided, which provides favorable conditions for promoting the synchronous phase change of bainite and sorbite later, specifically: the wire drawing temperature is controlled to be 895 DEG C.

[0038] The online molten salt semi-quenching process adopts two-stage salt bath tanks with molten salt inside. The wire rod after wire drawing is conveyed through the first-stage salt bath tank for front-stage molten salt treatment, so that the wire rod is cooled at a cooling rate of 35℃ / s, quickly passes through the interlaced carbide zone from the high-temperature austenite state into the mixed phase zone of bainite and pearlite, inhibits the formation of interlaced carbide and coarse pearlite, forms the microstructure mainly composed of a small part of quenched bainite and a large part of fine lamellar interlaced sorbite, promotes the dispersion of vanadium-containing carbide, and then is conveyed through the second-stage salt bath tank for rear-stage molten salt treatment, reduces the molten salt circulation amount, promotes the isothermal tempering of the quenched bainite and sorbite microstructure formed, avoids the coarsening of carbide, and adjusts the strength-plasticity matching of the wire rod. Specifically, the molten salt temperature of the front-stage molten salt treatment is 470℃, the treatment time is 75s, the molten salt circulation amount is 510t / h, and the molten salt temperature rise is ≤10℃; the molten salt temperature of the rear-stage molten salt treatment is 460℃, the treatment time is 315s, the molten salt circulation amount is 245t / h, and the molten salt temperature rise is ≤3℃.

[0039] The roller slow cooling process blows hot air ≥250℃ above the two-stage salt bath tanks of the online molten salt semi-quenching process to the conveying roller through controlling the opening degree of the heat preservation cover, conveys the wire rod through the heat preservation cover through the conveying roller, promotes the further toughening of the microstructure of the wire rod, and improves the tempering softening effect of the wire rod. Specifically, the wire rod is cooled to 275℃ at a slow cooling rate of 0.35℃ / s. Figure 2

[0040] Comparative Example 3: A manufacturing method of hot-rolled wire rod, which is different from that of Example 2 in that, during the front-stage molten salt treatment of the online molten salt semi-quenching process, the wire rod is cooled at a cooling rate of 37℃ / s, the molten salt temperature of the front-stage molten salt treatment is 450℃, the treatment time is 155s, and the hot-rolled wire rod product is obtained after being discharged.

[0041] Comparative Example 4: A manufacturing method of hot-rolled wire rod, which is different from that of Example 2 in that, during the front-stage molten salt treatment of the online molten salt semi-quenching process, the wire rod is cooled at a cooling rate of 33℃ / s, the molten salt temperature of the front-stage molten salt treatment is 500℃, the treatment time is 40s, and the hot-rolled wire rod product is obtained after being discharged. Example 3:

[0042] ​A preferred embodiment of the method for manufacturing the high-strength complex-phase hot-rolled wire rod for 2060 MPa grade stranded wire according to the present application has the chemical composition and mass percentage of C: 0.85%, Si: 0.47%, Mn: 0.81%, V: 0.024%, P: 0.015%, S: 0.014%, and the balance of Fe and inevitable impurities; and is manufactured according to the process flow of rolling → wire drawing → on-line molten salt semi-quenching → roller slow cooling → coiling, in particular: The rolling process is used to heat the steel billet with a specification of 220 mm x 220 mm to a high-temperature steel billet with a rolling plasticity by a heating furnace, reduce composition segregation, and avoid overburning; the steel billet is rolled into a wire rod with a diameter specification of 11 mm after the heating furnace by a rolling line; appropriate rolling temperature and reduction are selected; strain-induced precipitation of V pins is used to pin grain boundaries and refine grains; in particular, the soaking temperature of the heating furnace is controlled to be 1200℃, the in-furnace time is 185 min, the initial rolling temperature is 1095℃, the final rolling temperature is 915℃, and the final rolling reduction is 28.5%; the wire drawing process is used to draw the wire rod out of the rolling line into a wire rod through a wire drawing machine; the wire rod is scattered on a roller and conveyed along the roller; appropriate wire drawing temperature is selected to make the wire rod in a high-temperature austenite state, avoid the precipitation of network carbide at the wire drawing stage, and provide favorable conditions for promoting the synchronous phase change of bainite and sorbite later; in particular, the wire drawing temperature is controlled to be 905℃.

[0043] The on-line molten salt semi-quenching process adopts two-stage salt bath tanks with molten salt; the wire rod after wire drawing is conveyed through the first-stage salt bath tank for pre-stage molten salt treatment, so that the wire rod is cooled at a cooling rate of 37℃ / s, quickly passes through the network carbide interval from the high-temperature austenite state into the bainite and pearlite mixed phase interval, inhibits the formation of network carbide and coarse pearlite, and forms a structure mainly composed of a small part of quenched bainite and a large part of fine interlamellar spacing sorbite, promotes the dispersion precipitation of vanadium-containing carbide, and then is conveyed through the second-stage salt bath tank for post-stage molten salt treatment; the molten salt circulation amount is reduced, the quenched bainite and sorbite structure formed is subjected to isothermal tempering, and the coarsening of carbide is avoided to regulate the strength and plasticity matching of the wire rod; in particular, the molten salt temperature of the pre-stage molten salt treatment is 463℃, the treatment time is 115 s, the molten salt circulation amount is 590 t / h, and the molten salt temperature rise is ≤10℃; the molten salt temperature of the post-stage molten salt treatment is 465℃, the treatment time is 270 s, the molten salt circulation amount is 275 t / h, and the molten salt temperature rise is ≤3℃.

[0044] The roller slow cooling process adopts control of the opening of the heat preservation cover, and hot air with a temperature of ≥250℃ above the two salt bath tanks of the on-line molten salt semi-quenching treatment is blown to the conveying roller, and the wire rod is conveyed through the heat preservation cover by the conveying roller, so that the further toughening of the wire rod structure is promoted, and the temper softening effect of the wire rod is improved, and specifically: the wire rod is cooled to 272℃ at a slow cooling speed of 0.4℃ / s; the coiling process is used to coil the wire rod into a coil by the coiling drum, and the hot rolled wire rod product is obtained after packaging and storage, and the metallographic structure diagram is as shown in Figure 3

[0045] Comparative Example 5 A manufacturing method of a hot rolled wire rod, which is different from that of Example 3 in that the molten salt temperature of the second-stage molten salt treatment is 495℃, and the treatment time is 405s, and the hot rolled wire rod product is obtained after being discharged.

[0046] Comparative Example 6 A manufacturing method of a hot rolled wire rod, which is different from that of Example 3 in that the molten salt temperature of the second-stage molten salt treatment is 430℃, and the treatment time is 200s, and the hot rolled wire rod product is obtained after being discharged. Example 4

[0047] In a preferred embodiment of the manufacturing method of the 2060MPa high-strength composite hot rolled wire rod for the strand, the chemical composition and mass percentage of the hot rolled wire rod include C: 0.84%, Si: 0.45%, Mn: 0.85%, V: 0.03%, P: 0.013%, S: 0.015%, and the rest is Fe and inevitable impurities; and the manufacturing method is manufactured according to the process flow of rolling→ wire drawing→ on-line molten salt semi-quenching→ roller slow cooling→ coiling, and specifically: The rolling process is used to heat the steel billet with a specification of 220mm×220mm to a high-temperature steel billet with a rolling plasticity by a heating furnace, reduces the composition segregation and avoids overburning, and the steel billet is rolled into a wire rod with a diameter specification of 14mm by a rolling line after being discharged from the heating furnace, and the appropriate rolling temperature and reduction are selected, the strain induces the precipitation of V to pin the grain boundary and refine the grain, and specifically: the soaking temperature of the heating furnace is controlled to be 1210℃, the in-furnace time is 160min, the initial rolling temperature is 1100℃, the final rolling temperature is 930℃, and the final rolling reduction is 27%; the wire drawing process is used to draw the wire rod discharged from the rolling line into a wire rod by a wire drawing machine, the wire rod is scattered on the roller and conveyed along the roller, and the appropriate wire drawing temperature is selected to make the wire rod in the high-temperature austenite state, avoid the precipitation of net-shaped carbide at the wire drawing stage, and provide favorable conditions for the synchronous phase change of the bainite and sorbite later, and specifically: the wire drawing temperature is controlled to be 915℃.

[0048] ​The online molten salt semi-quenching process adopts two-stage salt bath tanks with molten salt inside. The wire rod after wire drawing is conveyed through the first-stage salt bath tank for front-stage molten salt treatment, so that the wire rod is cooled at a cooling rate of 40℃ / s, quickly passes through the interlaced carbide zone from the high-temperature austenite state into the mixed phase zone of bainite and pearlite, inhibits the formation of interlaced carbide and coarse pearlite, forms the microstructure mainly composed of a small part of quenched bainite and a large part of fine lamellar interlaced sorbite, promotes the dispersion of vanadium-containing carbide, and then is conveyed through the second-stage salt bath tank for rear-stage molten salt treatment, reduces the molten salt circulation amount, promotes the isothermal tempering of the quenched bainite and sorbite microstructure formed, avoids the coarsening of carbide, and adjusts the strength and plasticity matching of the wire rod. Specifically, the molten salt temperature of the front-stage molten salt treatment is 455℃, the treatment time is 150s, the molten salt circulation amount is 650t / h, and the molten salt temperature rise is ≤10℃; the molten salt temperature of the rear-stage molten salt treatment is 470℃, the treatment time is 210s, the molten salt circulation amount is 310t / h, and the molten salt temperature rise is ≤3℃.

[0049] The roller slow cooling process blows hot air ≥250℃ above the two-stage salt bath tanks of the online molten salt semi-quenching process to the conveying roller through controlling the opening degree of the heat preservation cover, conveys the wire rod through the heat preservation cover through the conveying roller, promotes the further toughening of the wire rod microstructure, and improves the tempering softening effect of the wire rod. Specifically, the wire rod is cooled to 270℃ at a slow cooling rate of 0.5℃ / s. The coiling process is used to coil the wire rod into a coil through a coiling drum, and the hot-rolled wire rod product is obtained after packaging and storage.

[0050] Comparative Example 7: A manufacturing method of a hot-rolled wire rod, which is different from the manufacturing method of Example 4 in that the manufacturing method is manufactured according to the process flow of rolling→wire drawing→online molten salt semi-quenching→air cooling. The air cooling process adopts opening the heat preservation cover and controlling the wire rod to be cooled to 265℃ at a slow cooling rate of 1.4℃ / s, and the hot-rolled wire rod product is obtained after offline.

[0051] The hot-rolled wire rods obtained in Examples 1-4 and Comparative Examples 1-7 above are subjected to microstructure and performance detection, and the comparison results are shown in Table 1 below: Table 1. Comparison results of microstructure and performance of different hot-rolled wire rod compositions and manufacturing methods

[0052] From the comparison results of Example 1 and Comparative Example 1, it can be seen that, compared with the simplified component system, the quenching penetrability of the wire rod decreases, and the cooling ability of the Stelmor air cooling line is limited, the wire rod slowly passes through the secondary cementite and pearlite precipitation temperature interval, and is easy to form network carbide, especially as the diameter specification of the wire rod decreases, the surface or local cooling is too fast to form low-temperature brittle structure, the core cooling is slow to easily cause the cementite to coarsen during the cooling process, the micro-alloyed carbide is insufficient and uneven, and it is difficult to fully play its strengthening effect, which will bring greater loss of strength and plasticity and mechanical property fluctuation. The present application combines the on-line molten salt semi-quenching technology on the basis of the component to inhibit the network carbide and coarse pearlite, and the microstructure includes the complex phase structure composed of tempered sorbite and tempered bainite, which can make up for the strength loss caused by the simplified component system, and adjust the strength and plasticity matching of the wire rod. From the results of Examples 1-4, it can be seen that the tensile strength is 1390-1440 MPa, the reduction of area is 32%-37%, and the wire rod is used for manufacturing 2060 MPa grade twisted wire and other application fields, which is beneficial to downstream drawing and twisting processing.

[0053] From the comparison results of Example 1 and Comparative Example 2, it can be seen that, the higher the wire drawing temperature is selected, the austenitizing of the wire rod is complete, the temperature is too low to form network carbide at the wire drawing stage, a temperature difference is formed with the molten salt temperature, and favorable conditions are provided for obtaining sufficient supercooling degree to promote the synchronous phase change of bainite and sorbite, and the limitation on the rolling temperature is reduced.

[0054] From the comparison results of Example 2 and Comparative Example 3, it can be seen that, the lower the molten salt temperature of the front-stage molten salt treatment is, the more conducive to inhibiting the formation of network carbide, and the more conducive to inhibiting the early precipitation of coarse pearlite and ferrite, promoting the preferential nucleation of bainite, reducing the interlamellar spacing of sorbite, and prolonging the treatment time, which can improve the dispersion precipitation driving force of vanadium-containing carbide, and promote the synchronous precipitation of nanoscale precipitates in the bainite and sorbite transformation process, thereby improving the strength of the matrix; but if the molten salt temperature is too low and the treatment time is too long, the bainite in the transformation product will increase, the sorbite transformation will be affected, the dislocation density and stress of the structure will be large, the softening difficulty and production energy consumption will be increased, and the plasticity of the structure and the production efficiency will be affected.

[0055] From the comparison results of Example 2 and Comparative Example 4, it can be seen that, the higher the molten salt temperature of the front-stage molten salt treatment is and the shorter the treatment time is, the more conducive to reducing the precipitation risk of martensite and other abnormal structures, promoting the sorbite transformation, reducing the stress and thermal stress of the structure, reducing the stress release difficulty, reducing the production energy consumption, and promoting rapid production, but if the molten salt temperature is too high and the treatment time is too short, it is not conducive to inhibiting network carbide and abnormal structures, the formation driving force of bainite and vanadium-containing carbide decreases, and the strength and uniformity of the matrix decrease.

[0056] From the comparison results of Example 3 and Comparative Example 4, it can be seen that the higher the molten salt temperature and the longer the treatment time of the later stage molten salt treatment, are beneficial to reduce the dislocation density of quenched bainite, promote the release of microstructure stress, promote the full dispersion of vanadium-containing carbide precipitation, and improve the overall plasticity and toughness, but if the molten salt temperature is too high and the treatment time is too long, the atomic diffusion ability is enhanced, the microstructure is excessively tempered and softened, which will cause strength loss, and the VC is easy to coarsen, which will cause strong plasticity loss and increase production energy consumption.

[0057] From the comparison results of Example 3 and Comparative Example 5, it can be seen that the lower the molten salt temperature and the shorter the treatment time of the later stage molten salt treatment, are beneficial to reduce the softening speed and production energy consumption, shorten the production time, inhibit the coarsening of the dispersed precipitated phase, and reduce the strength loss, but if the molten salt temperature is too low and the treatment time is too short, it is not conducive to isothermal tempering softening, the vanadium-containing carbide cannot be fully precipitated, and the microstructure stress cannot be fully released, which will cause strong plasticity loss.

[0058] From the comparison results of Example 4 and Comparative Example 7, it can be seen that the roller slow cooling can avoid the insufficient plasticity of the rod caused by insufficient slow cooling, and at the same time, the slow cooling promotes the further toughening of the rod structure and improves the tempering softening effect of the rod.

[0059] The above series of detailed descriptions are only specific descriptions of the feasible embodiments of the present application, and are not used to limit the protection scope of the present application. Any equivalent embodiments or changes made without departing from the spirit of the present application should be included in the protection scope of the present application.

Claims

1. A method for manufacturing high-strength multi-phase hot-rolled wire rod for 2060MPa grade stranded wire, characterized in that: The manufacturing method includes: The wire rod is produced by rolling according to the chemical composition of the hot-rolled wire rod, wherein the chemical composition and mass percentage of the hot-rolled wire rod include: C: 0.84%-0.88%, Si: 0.30%-0.47%, Mn: 0.65%-0.85%, V: 0.01%-0.03%, P≤0.015%, S≤0.015%, and the remainder is Fe and unavoidable impurities; after the wire rod is spun into a wire rod at a spinning temperature of ≥880°C, it is subjected to an online molten salt semi-quenching treatment, so that the wire rod is cooled at a cooling rate of ≥33°C / s, and enters a mixed phase region of bainite and pearlite from an austenite state, forming a structure mainly composed of quenched bainite and bainite structure, and then isothermally tempered, and finally slowly cooled by a roller to produce a hot-rolled wire rod with a microstructure including a dual-phase structure composed of tempered bainite and tempered bainite.

2. The method for manufacturing a high-strength multi-phase hot-rolled wire rod for 2060 MPa grade stranded wire according to claim 1, characterized in that: Before the rolling, the soaking temperature of the heating furnace is controlled to be 1170-1210° C., and the soaking time in the furnace is 160-250 minutes.

3. The method for manufacturing a high-strength multi-phase hot-rolled wire rod for 2060 MPa grade stranded wire according to claim 1, characterized in that: During the rolling, the initial rolling temperature is controlled to be 1065-1100° C., the final rolling temperature is controlled to be 890-930° C., and the final rolling reduction is controlled to be 27%-32%.

4. The method for manufacturing a high-strength multi-phase hot-rolled wire rod for 2060 MPa grade stranded wire according to claim 1, characterized in that: During the spinning process, the spinning temperature is controlled to be 880-915°C.

5. The method for manufacturing a high-strength multi-phase hot-rolled wire rod for 2060 MPa grade stranded wire according to claim 1, characterized in that: The online molten salt semi-quenching treatment is divided into a front-stage molten salt treatment and a rear-stage molten salt treatment. The molten salt temperature of the front-stage molten salt treatment is 455~485℃, the treatment time is 45~150s, and the molten salt circulation volume of the front-stage molten salt treatment is greater than the molten salt circulation volume of the rear-stage molten salt treatment; the molten salt temperature of the rear-stage molten salt treatment is 450~470℃, and the treatment time is 210~400s.

6. The method for manufacturing high-strength multi-phase hot-rolled wire rod for 2060 MPa grade stranded wire according to claim 5, characterized in that: The molten salt circulation rate of the front-stage molten salt treatment is 450~650t / h, and the molten salt temperature rise is ≤10°C; the molten salt circulation rate of the back-stage molten salt treatment is 200~310t / h, and the molten salt temperature rise is ≤3°C.

7. The method for manufacturing high-strength multi-phase hot-rolled wire rod for 2060 MPa grade stranded wire according to claim 5, characterized in that: The roller slow cooling controls the wire rod to be cooled to below 280° C. at a slow cooling rate of ≤0.5° C. / s for coiling.

8. A high-strength multi-phase hot-rolled wire rod for 2060 MPa grade stranded wire, characterized in that: The hot-rolled wire rod is manufactured by the method for manufacturing high-strength multi-phase hot-rolled wire rod for 2060 MPa grade stranded wire according to any one of claims 1 to 7.

9. The high-strength multi-phase hot-rolled wire rod for 2060 MPa grade stranded wire according to claim 8, characterized in that: The volume percentage of the tempered bainite is 65% to 75%, the interlamellar spacing is 65 to 110 nm, the volume percentage of the tempered bainite is 25% to 35%, the network carbide grade of the hot-rolled wire rod is grade 0, and the mechanical property same-circle difference is ≤40 MPa.

10. The high-strength multi-phase hot-rolled wire rod for 2060 MPa grade stranded wire according to claim 8, characterized in that: The hot-rolled wire rod has a diameter of 5.0-14.0 mm, a tensile strength of 1390-1440 MPa, and a cross-sectional shrinkage rate of 32%-37%.

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