A hot-rolled wire rod for 2400 MPa class bridge cables and its manufacturing method

Abstract

The present invention relates to a hot-rolled wire rod for 2400 MPa-class bridge cables and a manufacturing method thereof. After hot-rolling and coiling the wire rod with a high-carbon composition of Cr-Mo-V into a wire rod, it undergoes online molten salt rapid cooling and isothermal treatment, causing the wire rod to cool at a cooling rate of ≥32 °C / s, entering the sorbite phase region from the austenite state, forming a structure mainly composed of sorbite and controlling the precipitation and growth of carbides. At the same time, isothermal toughening is carried out to remove stress, and finally, slow cooling is carried out through a roller table to produce a hot-rolled wire rod with a mixed microstructure composed of tempered sorbite, ferrite, and pearlite with a melting point, which can improve the strength-ductility performance matching of the wire rod, reduce the fluctuation of mechanical properties, with a tensile strength of 1640~1680 MPa, an area reduction of 27%~32%, and a difference in mechanical properties within the same coil of ≤45 MPa, facilitating rapid and stable production, being used for the manufacture of 2400 MPa-class bridge cables, and being beneficial to reducing the risk of wire breakage.

Description

Technical Field

[0001] The present invention belongs to the technical field of hot-rolled wire rods, and particularly relates to a hot-rolled wire rod for bridge cables with a strength grade of 2400 MPa and a manufacturing method thereof. Background Art

[0002] After a long-span bridge is put into use, it not only has to bear the static load brought by its own weight, but also has to bear the dynamic load brought by vehicle passing and bad weather. Therefore, long-span bridges are constantly developing towards the direction of light weight and ultra-high strengthening of bridge cables, and extremely high requirements are imposed on the strength and plasticity of bridge cables for long-span bridges. The ultra-high strengthening of bridge cables means the ultra-high strengthening of the base material wire rods for bridge cables. Existing base material wire rods for bridge cables often adopt alloying combined with an air-cooling line for development. There are still the following technical difficulties in manufacturing hot-rolled wire rods for 2400 MPa grade bridge cables with higher strength and plasticity and smaller mechanical property fluctuations:

[0003] First, in order to improve the strength of the wire rod for bridge cables, the degree of alloying of the wire rod components is relatively high. For example, a high-strength and high-toughness bridge cable steel and a preparation method thereof disclosed in Patent CN110144521B adopt a C-Si-Mn-Co-V composition design for the wire rod to produce bridge cable steel with a tensile strength ≥ 2400 Mpa. However, on the one hand, although the low-carbon composition can reduce the difficulty of controlling network carbide on the air-cooling line for the wire rod, the alloy component content is relatively high, resulting in a relatively high material cost. On the other hand, the high-silicon, high-manganese, and high-aluminum components make the risk of deteriorating structures such as martensite on the air-cooling line for the hot-rolled wire rod extremely high, which will lead to insufficient plasticity and toughness of the wire rod, large internal stress and mechanical property fluctuations, and easily induce wire breakage problems during the wire drawing process of the wire rod.

[0004] Second, in order to take into account the material cost and improve the drawing performance of the wire rod, the wire rod for high-strength bridge cables in the prior art mostly adopts high-carbon pearlite steel. For example, the patent CN118880169A discloses a wire rod for high-strength bridge cables and its production method, which adopts 87SiMn component combined with low-temperature rolling and spinning, Stelmor air-cooled line cooling and more than 120 minutes of insulation corridor insulation to make a high sorbitization rate wire rod with a strength of more than 1400MPa, which is used for 2200~2300MPa strength level bridge cables. However, on the one hand, the 2400MPa-level bridge cables have higher requirements on the strength of the hot-rolled wire rod parent material. If the wire rod strength is insufficient, it is necessary to increase the drawing passes to improve the material strength. The plastic loss is large in the process, and the risk of wire breakage is prone to occur. In addition, the galvanizing process after drawing will bring a certain strength loss, and it is difficult to reach the 2400MPa-level bridge cable grade. In order to further strengthen the material, the carbon, silicon, manganese and other elements in the organization are further increased, which will increase the carbon element and alloy in the steel billet. Gold element segregation. Due to the limited maximum cooling capacity of the Stelmor air-cooling line, network carbides that are unfavorable to plasticity and organizational uniformity are more likely to form in the wire rod, and the cooling control capacity of the air-cooling line is unstable. In order to minimize the impact of network carbides and increase the air-cooling intensity, the temperature difference from the surface of the wire rod to the core will be further increased. Affected by segregation, the parts of the wire rod surface that cool too quickly are more likely to form hard and brittle abnormal organizations such as martensite, which increases the fluctuation of the mechanical properties of the wire rod and induces the problem of wire breakage during the wire rod drawing process. On the other hand, during the continuous cooling process, the wire rod passes through the phase transition temperature range for a short time, and the insufficient phase transition of the austenite organization will cause the wire rod to continue to form abnormal organizations during the subsequent cooling process. As the carbides coarsen and lose strong plastic properties during the phase transition, the wire rod is already in a low temperature state after the phase transition, which will increase the difficulty of softening. The organizational stress of the resulting troostite phase is also large, which will lead to insufficient plasticity of the wire rod. Long-term heat preservation will also make the wire rod online for too long, affecting production efficiency and cost. Summary of the invention

[0005] The present invention aims to solve at least one of the above-mentioned technical problems to a certain extent. The present invention provides a 2400MPa-grade hot-rolled wire rod for bridge cables and a manufacturing method thereof, which can improve the strength-plasticity matching of the wire rod, reduce the fluctuation of mechanical properties, facilitate rapid and stable production, and be used for the manufacture of 2400MPa-grade bridge cables, which is beneficial to reducing the risk of wire breakage.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A method for manufacturing a 2400MPa grade hot-rolled wire rod for bridge cables, the manufacturing method comprising:

[0008] The wire rod is rolled according to the chemical composition of the hot-rolled wire rod. The chemical composition and mass percentage of the hot-rolled wire rod include: C: 0.94% - 0.97%, Si: 0.70% - 0.90%, Mn: 0.85% - 1.05%, Cr: 0.57% - 0.67%, V: 0.040% - 0.055%, Mo: 0.25% - 0.45%, P ≤ 0.015%, S ≤ 0.015%, and the rest are Fe and inevitable impurities. After the wire rod is spun at a spinning temperature of ≥ 930 °C to form a wire rod, it undergoes on-line molten salt rapid cooling and isothermal treatment, so that the wire rod cools at a cooling rate of ≥ 32 °C / s, enters the sorbite phase region from the austenite state, forms a structure mainly composed of sorbite, controls the precipitation and growth of carbides, and at the same time isothermally toughens and relieves stress. Finally, it is slowly cooled through a roller table to produce a hot-rolled wire rod with a microstructure composed of tempered sorbite, ferrite, and eutectoid pearlite.

[0009] The design basis for the chemical composition and mass percentage of the above hot-rolled wire rod includes:

[0010] (1) Carbon: The C element is an effective carbide strengthening element and austenite forming element, which is more economical than other elements. As the carbon content increases, the phase transformation temperature will decrease, the bainite transformation will be delayed, the sorbite phase transformation in the on-line molten salt rapid cooling and isothermal treatment process will be promoted, the material strength will be improved, and the hot-rolled wire rod will have higher load-bearing capacity after being drawn into a steel wire to make a bridge cable. However, as the carbon content increases, the carbon segregation tendency during the solidification of the steel billet will increase, the decarburization and the precipitation tendency of network carbides will increase, and the difficulty of controlling abnormal structures will increase, which is not conducive to the control of carbide precipitation. Therefore, in order to meet the high-strength requirements of the 2400 MPa grade bridge cable for the hot-rolled wire rod base material, control the material cost, and at the same time reduce the difficulty of controlling network carbides and carbide precipitation, the mass percentage of C is controlled at 0.94% - 0.97%.

[0011] (2) Silicon: The Si element is a good deoxidizer and can also inhibit the grain coarsening during the on-line molten salt rapid cooling and isothermal treatment, shift the phase transformation curve to the right, and inhibit the diffusion of carbon in austenite, so as to quickly obtain a sorbite structure mainly composed of fine lamellar spacing and improve the matrix strength. However, too high a silicon content will make the steel more prone to decarburization during high-temperature heating, increase the risk of abnormal structure precipitation, reduce the toughness and tissue uniformity of the steel, and is not conducive to drawing. At the same time, it increases the phase transformation temperature of the steel and is not conducive to the control of the dispersion precipitation of vanadium-containing carbides in the sorbite phase region. Therefore, in order to regulate the phase transformation temperature, promote the sorbite phase transformation, and facilitate the control of carbide precipitation and growth, the Si content is appropriately increased, and the mass percentage of Si is controlled at 0.70% - 0.90%.

[0012] (3) Manganese: Mn has a strong affinity with carbon, can expand the austenite phase region, increase the stability of austenite, and at the same time increase the hardenability of the wire rod, lower the phase transformation temperature. Thus, it is beneficial to promote the rapid nucleation of sorbite structure mainly with fine lamellar spacing and the dispersed precipitation of vanadium carbides during the online molten salt rapid cooling and isothermal treatment, thereby increasing the tensile strength of the wire rod. When the bridge cable bears tensile force, it can resist impact and vibration loads. However, when the content of Mn is too high, it will exacerbate the segregation of alloying elements, increase the precipitation risk of low-temperature structures such as bainite and martensite in the wire rod, and at the same time reduce the activity of carbon, increasing the difficulty of isothermal toughening and stress relief, and thus losing the plasticity of the wire rod. Therefore, in order to make the hot-rolled wire rod have higher strength, reduce the difficulty of controlling tissue uniformity, tempering, and carbide precipitation, the content of Mn is appropriately increased, and the mass percentage of Mn is controlled at 0.85% - 1.05%.

[0013] (4) Chromium: The element Cr is a strong carbide-forming element, which can refine grains, improve the hardenability of steel, increase the stability of austenite, shift the phase transformation curve to the right, is beneficial to the formation of sorbite structure during cooling, is beneficial to improving the matrix strength, and reduces the strength loss during the subsequent hot-dip galvanizing process of wire drawing for cable making. However, when the content of Cr is too high, it will exacerbate the composition segregation, increase the precipitation risk of abnormal martensite structure, affect the tissue uniformity of the wire rod, and significantly increase the difficulty of improving the plasticity of the wire rod, affecting the effect of isothermal toughening and stress relief, and thus affecting the wire drawing and torsion properties of the wire. The coarsening of Cr precipitation will also result in the loss of strength and plasticity, causing cracks and drawing fractures. Therefore, in order to improve the material strength and facilitate the control of carbide precipitation, the mass percentage of Cr is controlled at 0.57% - 0.67%.

[0014] (5) Vanadium: As a microalloying element, the element V can inhibit the coarsening of high-temperature austenite and hinder the growth of austenite grains, thereby refining grains. At the same time, it can disperse and precipitate during the isothermal process. The fine and dispersed vanadium precipitation phases can pin dislocations and grain boundaries, hinder dislocation movement and grain growth, effectively increase the strength of the hot-rolled wire rod without reducing plasticity. However, the cost of the element V is relatively high. Excessive addition is not conducive to controlling the cost of the wire rod and has a coarsening risk. When the vanadium precipitation phases coarsen, the hindering effect on dislocations and grain boundaries weakens, dislocations are more likely to bypass the precipitation phases, and the strength of the wire rod decreases accordingly. At the same time, the coarsened vanadium precipitation phases may become crack sources, reducing the toughness of the material. Therefore, based on the role and cost of the element V, the content of the element V in the present invention is controlled at 0.040% - 0.055%.

[0015] (6) Molybdenum: The element Mo can improve the hardenability of steel, increase the stability of supercooled austenite, shift the C curve to the right, slow down the transformation of austenite to ferrite, and effectively inhibit the coarsening of carbide precipitation phases, effectively enhancing the strengthening effect of precipitation phases and maintaining a relatively high strength during tempering. However, due to the high price of the element Mo, based on the role and cost of the element Mo, the mass percentage of Mo is controlled at 0.25% - 0.45%.

[0016] (7) Phosphorus and sulfur: The P element and S element belong to impurity elements, and the lower the better. Therefore, P ≤ 0.015% and S ≤ 0.015% are controlled.

[0017] The above hot-rolled wire rods adopt a high-carbon chemical composition design of Cr-Mo-V, and by optimizing the Si, Mn, and Cr components, the C curve and the phase transformation temperature are further regulated, providing favorable conditions for promoting the nucleation of sorbite with finer lamellar spacing, reducing the difficulty of controlling carbide precipitation and growth, and reducing the difficulty of abnormal structure and isothermal stress relief during the online molten salt rapid cooling and isothermal treatment of the wire rods. On this basis, a relatively high spinning temperature is selected to avoid the formation of network carbides during the spinning stage due to low-temperature spinning, and at the same time, it is convenient to improve the strength-plasticity matching of the material with a relatively high quenching temperature. The wire rods after spinning are not air-cooled but are treated by online molten salt rapid cooling and isothermal treatment:

[0018] I. Compared with the limited maximum cooling capacity of the Stelmor air-cooling line and the uncontrollable cooling rate of the wire rods, which result in abnormal structures such as network carbides and martensite and affect the refinement of sorbite lamellae. On the one hand, online molten salt rapid cooling and isothermal treatment can utilize the high heat transfer capacity of the molten salt to promote the rapid cooling of the wire rods from the high-temperature austenite state, quickly pass through the secondary cementite precipitation temperature range of 700 - 800 °C, and avoid the formation of network carbides in the structure, which would damage the tissue uniformity and increase the brittleness of the wire rods. On the other hand, in combination with a relatively high spinning temperature, the hardenability of the wire rods, and the inhibition of grain coarsening by Si, the wire rods can quickly enter the sorbite phase region for quenching, forming a large supercooling degree, thereby promoting the incubation of sorbite phase transformation and forming a structure mainly composed of sorbite with fine lamellar spacing to make up for the adverse effect of the longer time required for the transformation of supercooled austenite after the C curve shifts to the right. Furthermore, the material strength is improved and the online time is reduced. At the same time, when the wire rods pass through the molten salt, the molten salt can cover the surface of the wire rods for rapid and uniform heat transfer, and there is no temperature difference problem between the windward side and the leeward side, which can further reduce the temperature difference from the edge to the core of the wire rod cross-section, and thus avoid the formation of martensite abnormal structure that is unfavorable to tissue uniformity and drawing, improve the control problem of abnormal structure caused by high alloy content and element segregation, and reduce the mechanical property fluctuation.

[0019] Second, compared with the limited minimum cooling capacity of the Stelmor air-cooled line, the uncontrollable cooling rate of the wire rod, and the weakening of the carbide strengthening effect due to the continuous cooling of the wire rod, the content of the obtained sorbite structure is not high and the plasticity is insufficient. On the one hand, after the wire rod is treated by molten salt, it can be kept consistent with the molten salt temperature. Compared with the continuous cooling of the wire rod, it can extend the time of the wire rod at the peak precipitation temperature of sorbite, promote the full transformation of austenite into sorbite structure, reduce the ferrite content, and improve the matrix strength. It can also promote the massive precipitation of carbides in the medium-temperature range, cooperate with Mo to inhibit the coarsening of the carbide precipitation phase, avoid the simultaneous formation of coarser and finer precipitation phases due to the uncontrollable cooling rate and continuous cooling of the wire rod, and then take into account the tissue uniformity, effectively improve the strengthening effect of the precipitation phase, and improve the matrix strength. On the other hand, the temperature in the sorbite phase region is relatively high, which can extend the time of the wire rod in the isothermal range at a higher temperature, perform high-temperature isothermal toughening treatment on the sorbite structure obtained by quenching, promote the lamination melting of the sorbite structure to form fused pearlite, and temper to form a tempered sorbite structure with better plasticity, reduce the tissue stress, and improve the strength-plasticity matching of the wire rod. The long-time heat preservation in the heat preservation corridor can also reduce the on-line time of the wire rod and promote the rapid offline of the wire rod. The temperature of the wire rod is relatively high after the on-line molten salt rapid cooling and isothermal treatment, which reduces the cooling rate of the wire rod, can prevent the stress increase caused by the too-fast cooling of the wire rod during the cooling process, and further promote the toughening of the wire rod tissue, realizing tissue regulation and high strength-plasticity matching of the wire rod.

[0020] Selecting a relatively high soaking temperature and soaking time in the heating furnace before rolling can promote the uniform diffusion of alloying elements in the billet, reduce the deformation resistance of the material, and prepare for rolling. In the preferred technical solution, before rolling, the soaking temperature of the heating furnace is controlled at 1180-1240 °C, and the soaking time ≥ 150 min.

[0021] Due to the relatively high spinning temperature, the limitation on the rolling temperature can be reduced. Selecting a relatively high initial rolling temperature can reduce the rolling force, enable the billet to deform more uniformly when stressed, cooperate with the finishing rolling temperature and finishing rolling reduction, promote the dynamic recrystallization during the finishing rolling process, refine the grains, and improve the strength and toughness of the matrix. In the preferred technical solution, during rolling, the initial rolling temperature is controlled at 1060-1100 °C, the finishing rolling temperature is controlled at 900-950 °C, and the finishing rolling reduction is 23%-29%.

[0022] In the preferred technical solution, the online molten salt rapid cooling and isothermal treatment is divided into a front-stage treatment and a rear-stage treatment. The molten salt temperature in the front-stage treatment is 555 - 580 °C, and the treatment time is 25 - 35 s. The molten salt circulation volume in the front-stage treatment is greater than that in the rear-stage treatment. The lower the molten salt temperature and the longer the treatment time in the front-stage treatment, the larger the degree of undercooling can be formed, which promotes the full transformation of the high-temperature austenite structure into a sorbite structure with finer lamellar spacing, provides more driving force for the dispersed precipitation of vanadium-containing carbides, and improves the matrix strength. However, if the molten salt temperature in the front-stage treatment is too low, there is a risk of precipitating bainite structure, and at the same time, it is lower than the medium-temperature range for the precipitation of vanadium-containing carbides, which is not conducive to carbide precipitation. If the treatment time is too long, the holding time of the larger molten salt circulation volume increases, increasing production energy consumption; on the contrary, if the molten salt temperature in the front-stage treatment is higher and the treatment time is shorter, the quenching cooling rate decreases, and the production energy consumption of the wire rod decreases. However, if the molten salt temperature is too high and the treatment time is too short, it is not conducive to the rapid phase transformation of high-temperature austenite to sorbite, the sorbite lamellar spacing increases, increasing the difficulty of wire breaking and losing matrix strength. Therefore, the molten salt temperature and treatment time in the front-stage treatment can be controlled to promote the phase transformation of the wire rod to form a structure mainly composed of sorbite with fine lamellar spacing, taking into account production energy consumption and making organizational preparations for the rear-stage treatment.

[0023] Since the temperature difference between the wire rod cooling from the laying temperature to the sorbite phase region is relatively large, selecting a larger molten salt circulation volume can control the molten salt temperature rise, improve tissue uniformity, and reduce the mechanical property fluctuation of the wire rod. In the preferred technical solution, the molten salt circulation volume in the front-stage treatment is 500 - 700 t / h, and the molten salt temperature rise ≤ 8 °C.

[0024] In the preferred technical solution, the molten salt temperature in the rear-stage treatment is 560 - 570 °C, and the treatment time is 150 - 250 s. The lower the molten salt temperature in the rear-stage treatment, the lower the tendency of carbide precipitation and growth can be reduced, promoting the dispersed precipitation of vanadium-containing carbides. However, if the molten salt temperature is too low, it is difficult to provide more thermal energy for isothermal toughening and stress relief, affecting the plasticity of the wire rod; on the contrary, if the molten salt temperature in the rear-stage treatment is higher, more lamellar fusing occurs, the stress relief softening effect is better, and the plasticity of the wire rod is improved. However, if the molten salt temperature is too high, it affects the precipitation of vanadium-containing carbides, the carbides precipitate and coarsen, and the strength loss accelerates, which is not conducive to the strength and plasticity performance; the longer the treatment time in the rear-stage treatment, the more the toughening and stress relief effect increases. However, if the treatment time is too long, there is a risk of carbide coarsening and excessive strength loss; on the contrary, if the treatment time in the rear-stage treatment is shorter, the isothermal toughening effect decreases. However, if the treatment time is too short, the carbides do not have enough time to precipitate fully and there is a high stress in the structure, resulting in loss of strength and plasticity performance. Therefore, the molten salt temperature and treatment time in the rear-stage molten salt can be further controlled to control the full dispersed precipitation of carbides, perform isothermal toughening on the quenched structure, and improve the strength-plasticity matching of the wire rod.

[0025] For the post-treatment section, selecting an appropriate molten salt circulation rate can reduce production energy consumption. Meanwhile, it can avoid too small a molten salt circulation rate, precisely control the temperature, reduce the temperature rise of the molten salt, further control the precipitation of carbides and the tempering effect. In the preferred technical solution, the molten salt circulation rate in the post-treatment section is 150 - 250 t / h, and the temperature rise of the molten salt ≤ 3°C.

[0026] Since the wire rod undergoes full phase transformation after online rapid isothermal treatment with molten salt, it can prevent the continued transformation of retained austenite into martensite. Selecting an appropriate cooling rate for the roller table slow cooling can prevent the stress increase caused by too fast a cooling rate during the cooling process of the wire rod, promote the further toughening of the wire rod structure, improve the softening effect of the wire rod and quickly offline. In the preferred technical solution, the roller table slow cooling controls the wire rod to slowly cool at a cooling rate of 0.5 - 1°C / s to below 300°C.

[0027] A hot-rolled wire rod for 2400 MPa-class bridge cables, which is manufactured by the manufacturing method of the hot-rolled wire rod for 2400 MPa-class bridge cables described in any one of the above.

[0028] The above hot-rolled wire rod adopts the Cr-Mo-V chemical composition design combined with the online molten salt rapid cooling isothermal technology, and is made into a mixed microstructure composed of tempered sorbite, ferrite and broken pearlite. Compared with traditional pearlitic high-carbon steel, the lamellar spacing of sorbite is finer than that of pearlite, and the strength and drawing hardening ability are higher. After the sorbite structure undergoes isothermal toughening tempering to transform into tempered sorbite and broken pearlite, the tissue stress is reduced, the toughness and plasticity are significantly improved, and the comprehensive mechanical properties are better. Through online molten salt rapid cooling isothermal treatment, the network carbide and martensite abnormal structures are effectively controlled. The full phase transformation of sorbite reduces the proportion of soft-phase ferrite in the tissue. At the same time, the carbides can be precipitated dispersedly to avoid coarsening, which can improve the strengthening effect of carbon, V and Cr elements and the tissue uniformity, enhance the strength-plasticity performance matching of the wire rod, and reduce the mechanical property fluctuation of the wire rod.

[0029] The finer the lamellar spacing of the tempered sorbite, the higher the matrix strength. In the preferred technical solution, the lamellar spacing of the tempered sorbite is 70 - 100 nm, and the volume percentage of the tempered sorbite ≥ 74%.

[0030] The higher the volume percentage of the tempered sorbite and the broken pearlite, the better the strength-plasticity performance. In the preferred technical solution, the volume percentage of the tempered sorbite and the broken pearlite ≥ 94%, and the volume percentage of the broken pearlite is 16% - 20%.

[0031] In the preferred technical solution, the network carbide grade of the hot-rolled wire rod is 0 grade, which can avoid the network carbide weakening the bonding force between metals and the adverse effect of the network carbide on plasticity.

[0032] The microstructure uniformity of the hot-rolled wire rod is improved, and abnormal microstructures such as network carbide and martensite are avoided. The mechanical property fluctuation is smaller. In the preferred technical solution, the mechanical property difference within the same coil of the hot-rolled wire rod is ≤45 MPa.

[0033] In the preferred technical solution, the diameter of the hot-rolled wire rod is 10.0 - 16.0 mm, the tensile strength is 1640 - 1680 MPa, and the reduction of area is 27% - 32%. The hot-rolled wire rod has a high tensile strength and good reduction of area, which can reduce the drawing exemption rate and plastic loss during the process, reduce the fracture risk during drawing and torsion, and is beneficial to the stable manufacture of 2400 MPa grade bridge cables.

[0034] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0035] (1) Aiming at the current situation that the wire rod for existing bridge cables has a high degree of alloying, and there is a very high risk of deteriorated microstructures such as network carbide and martensite on the air-cooling line, which is likely to induce wire breakage problems during the wire drawing process of the wire rod. The present invention combines the Cr-Mo-V chemical composition design with the online molten salt rapid cooling and isothermal technology. With a relatively high quenching temperature and molten salt control, the wire rod rapidly passes through the network carbide formation range from the high-temperature austenite state into the sorbite phase region, forming a microstructure mainly composed of fine lamellar spacing sorbite, and controlling the precipitation and growth of carbides in the isothermal range at a relatively high temperature. It can avoid the appearance of abnormal martensite microstructure, improve the strengthening effect of carbon elements, promote the dispersion precipitation of vanadium-containing carbides during isothermal process, inhibit the coarsening of precipitation phases of V and Cr carbides, enhance the strengthening effect of precipitation phases, and at the same time perform high-temperature isothermal toughening and stress relief treatment on the sorbite microstructure obtained by quenching. Finally, slow cooling on the roller table prevents stress increase and promotes further toughening of the wire rod microstructure, which can improve the strength-plasticity performance matching of the wire rod, reduce the mechanical property fluctuation, facilitate rapid and stable production, and has good industrial adaptability.

[0036] (2) Aiming at the current situation that the ultra-high strengthening of existing bridge cables is restricted by the base wire rod and it is difficult to meet the stable production of 2400 MPa grade bridge cables. The hot-rolled wire rod microstructure of the present invention includes a mixed microstructure composed of tempered sorbite, ferrite and eutectoid pearlite, which can improve the strengthening effect of carbon, V and Cr elements and microstructure uniformity, enhance the strength-plasticity performance matching of the wire rod, reduce the mechanical property fluctuation of the wire rod, reach a product tensile strength of 1640 - 1680 MPa and a reduction of area of 27% - 32%, and is used in application fields such as manufacturing 2400 MPa grade ultra-high strength bridge cables. It can reduce the fracture risk during drawing and torsion, promote the stable production of bridge cables, and has good market application prospects. Brief Description of the Drawings

[0037] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, wherein:

[0038] Figure 1 is the metallographic structure diagram of Embodiment 1 of the present invention;

[0039] Figure 2 is the metallographic structure diagram of Embodiment 2 of the present invention;

[0040] Figure 3 is the metallographic structure diagram of Embodiment 3 of the present invention. Detailed implementation manners

[0041] The embodiments described below with reference to the drawings are exemplary, solely for the purpose of illustration and do not limit the description of the features and characteristics of the present invention. To present the best mode of implementing the present invention, it is intended to explain the present invention and be sufficient for those skilled in the art to implement the present invention. It should not be construed as having any limitation on the scope of the present invention, which is only defined by the appended claims; the organization and performance detection of the hot-rolled wire rods obtained in the following embodiments and comparative examples include: the tensile test is carried out in accordance with "GB-T 228.1-2021 Metallic materials-Tensile testing-Part 1: Method of test at room temperature" to obtain the tensile strength and reduction of area; the microstructure detection is carried out in accordance with the metallic microstructure detection method of the GB / T13298 standard; the method for testing the difference in mechanical properties within the same coil: Take 2 coils of wire rods at 5 m from the end of the coil. With the lap joint area as the base point, each coil of wire rod is evenly divided into 8 segments on average, and 1 tensile specimen is taken on each segment. The strength range of the tensile specimens after the tensile test is the difference in mechanical properties within the same coil. Embodiment 1:

[0042] A preferred implementation manner of the manufacturing method of the 2400 MPa grade hot-rolled wire rod for bridge cables according to the present invention. The chemical composition and mass percentage of the hot-rolled wire rod include C: 0.95%, Si: 0.88%, Mn: 1.05%, Cr: 0.67%, V: 0.043%, Mo: 0.33%, P: 0.014%, S: 0.015%, and the rest are Fe and inevitable impurities; its manufacturing method is manufactured according to the technological process of rolling → wire laying → online molten salt rapid cooling and isothermal treatment → slow cooling on the roller table → coiling. Specifically:

[0043] The rolling process is used to heat a billet with a specification of 220mm×220mm into a hot billet with rollable plasticity through a heating furnace, promoting the homogenization of alloy components. After the billet exits the heating furnace, it is rolled into wire rods with a diameter specification of 16mm through a rolling line, promoting dynamic recrystallization and grain refinement during the finishing rolling process. Specifically: control the soaking temperature of the heating furnace at 1225°C, the residence time in the furnace at 160 min, the initial rolling temperature at 1090°C, the finishing rolling temperature at 940°C, and the finishing rolling reduction at 23%; The wire laying process is used to make the wire rods exiting the rolling line into coils through a wire laying machine. The coils are scattered on the roller table and transported along the roller table, keeping the coils in a high-temperature austenite state, with a relatively high quenching temperature, providing favorable conditions for forming a large supercooling degree later, promoting the refinement of the lamellar structure of the sorbite tissue and rapid nucleation. Specifically: control the wire laying temperature at 945°C.

[0044] The on-line molten salt rapid cooling and isothermal treatment process uses a two-stage salt bath tank with molten salt inside. The coils after wire laying are transported through the first-stage salt bath tank by the roller table for the front-stage treatment, cooling the coils at a cooling rate of 37°C / s, quickly passing through the reticulated carbide precipitation range from the high-temperature austenite state into the sorbite phase region, forming a structure mainly composed of fine lamellar spacing sorbite. Then the coils are transported through the second-stage salt bath tank by the roller table for the back-stage treatment. The molten salt circulation volume in the back-stage treatment is appropriately reduced, precisely controlling the temperature and reducing production energy consumption, controlling the coils in the isothermal range and controlling the precipitation and growth of carbides. At the same time, high-temperature isothermal toughening and stress relief treatment are carried out on the sorbite tissue obtained by quenching, improving the strength-plasticity matching of the coils. Specifically: the molten salt temperature in the front-stage treatment is 566°C, the treatment time is 27 s, the molten salt circulation volume is 645 t / h, and the molten salt temperature rise ≤ 8°C; the molten salt temperature in the back-stage treatment is 563°C, the treatment time is 225 s, the molten salt circulation volume is 180 t / h, and the molten salt temperature rise ≤ 3°C.

[0045] The roller table slow cooling process uses a non-fully closed heat preservation cover to transport the coils passing through the second-stage salt bath tank by the conveying roller table, preventing the stress of the coils from increasing due to too fast cooling rate during the cooling process, and promoting the further toughening of the coil structure, improving the softening effect of the coils. Specifically: control the coils to slowly cool to 284°C at a cooling rate of 1°C / s; The coiling process is used to coil the coils into coil reels through a coiling drum, and after packaging and warehousing, hot-rolled coil products are obtained. The metallographic structure diagram is as Figure 1 shown.

[0046] Comparative Example 1:

[0047] A manufacturing method of hot-rolled coils, the difference between its manufacturing method and that of Example 1 lies in: controlling the wire laying temperature at 900°C. When the on-line molten salt rapid cooling and isothermal treatment is carried out, the coils pass through the front-stage treatment, cooling the coils at a cooling rate of 31°C / s, and hot-rolled coils are obtained after leaving the line. Example 2:

[0048] A preferred embodiment of the manufacturing method of the hot-rolled wire rod for 2400MPa-class bridge cables according to the present invention. The chemical composition and mass percentage of the hot-rolled wire rod include C: 0.95%, Si: 0.7%, Mn: 0.95%, Cr: 0.64%, V: 0.04%, Mo: 0.25%, P: 0.014%, S: 0.01%, and the rest are Fe and inevitable impurities. Its manufacturing method is carried out according to the technological process of rolling → wire laying → on-line molten salt rapid cooling and isothermal treatment → slow cooling on the roller table → coiling. Specifically:

[0049] The rolling process is used to heat the steel billet with a specification of 220mm×220mm into a high-temperature steel billet that reaches the plastic state for rolling, promoting the homogenization of alloy components. After the steel billet exits the heating furnace, it is rolled into a wire rod with a diameter specification of 10mm through the rolling line, promoting dynamic recrystallization and grain refinement during the finishing rolling process. Specifically: control the soaking temperature of the heating furnace to be 1180°C, the residence time in the furnace to be 180min, the initial rolling temperature to be 1060°C, the finishing rolling temperature to be 900°C, and the finishing rolling reduction to be 29%. The wire laying process is used to make the wire rod exiting the rolling line into a wire coil through the wire laying machine. The wire coil is scattered on the roller table and transported along the roller table, making the wire coil in the high-temperature austenite state, providing favorable conditions for forming a large supercooling degree, promoting the refinement of the lamellar structure of the sorbite and rapid nucleation at a relatively high quenching temperature. Specifically: control the wire laying temperature to be 930°C.

[0050] The on-line molten salt rapid cooling and isothermal treatment process uses a two-stage salt bath tank with molten salt inside. The wire coil after wire laying is transported through the first-stage salt bath tank by the roller table for pre-treatment, making the wire coil cool down at a cooling rate of 32°C / s, quickly skipping the network carbide precipitation range from the high-temperature austenite state and entering the sorbite phase region, forming a structure mainly composed of fine lamellar spacing sorbite. Then the wire coil is transported through the second-stage salt bath tank by the roller table for post-treatment. The molten salt circulation volume in the post-treatment is appropriately reduced, accurately controlling the temperature and reducing production energy consumption, controlling the wire coil in the isothermal interval and controlling the precipitation and growth of carbides, and at the same time performing high-temperature isothermal toughening and stress relief treatment on the quenched sorbite structure to improve the strength-plasticity matching of the wire coil. Specifically: the molten salt temperature in the pre-treatment is 580°C, the treatment time is 35s, the molten salt circulation volume is 500t / h, and the molten salt temperature rise ≤ 8°C; the molten salt temperature in the post-treatment is 570°C, the treatment time is 150s, the molten salt circulation volume is 250t / h, and the molten salt temperature rise ≤ 3°C.

[0051] For the roller table slow cooling process, the heat preservation cover is not fully closed, and the wire rods passing through the second salt bath tank are conveyed by the conveying roller table to prevent the stress of the wire rods from increasing due to too fast cooling rate during the cooling process, and to promote the further toughening of the wire rod structure and improve the softening effect of the wire rods. Specifically: control the wire rods to be slowly cooled at a cooling rate of 0.5 °C / s to 295 °C; the coiling process is used to coil the wire rods into coils by a coiling drum, and after packaging and warehousing, the finished hot-rolled wire rods are obtained. The metallographic structure diagram is as shown in Figure 2 shown.

[0052] Comparative Example 2:

[0053] A manufacturing method of hot-rolled wire rods, the difference in its manufacturing method from that of Example 2 is that: the molten salt temperature in the front-stage treatment is 595 °C, the treatment time is 10 s, and the hot-rolled wire rods are obtained after being taken off the production line.

[0054] Comparative Example 3:

[0055] A manufacturing method of hot-rolled wire rods, the difference in its manufacturing method from that of Example 2 is that: the molten salt temperature in the front-stage treatment is 520 °C, the treatment time is 50 s, and the hot-rolled wire rods are obtained after being taken off the production line. Example 3:

[0056] A preferred implementation manner of the manufacturing method of the 2400 MPa grade bridge cable hot-rolled wire rods of the present invention, the chemical composition and mass percentage of the hot-rolled wire rods include C: 0.94%, Si: 0.82%, Mn: 0.9%, Cr: 0.57%, V: 0.052%, Mo: 0.41%, P: 0.015%, S: 0.015%, and the rest are Fe and inevitable impurities; its manufacturing method is manufactured according to the technological process of rolling → wire laying → on-line molten salt rapid cooling and isothermal treatment → roller table slow cooling → coiling. Specifically:

[0057] The rolling process is used to heat the steel billet with a specification of 220 mm × 220 mm into a high-temperature steel billet that reaches the plastic state for rolling through a heating furnace to promote the homogenization of alloy components. After the steel billet exits the heating furnace, the steel billet is rolled into a wire rod with a diameter specification of 12 mm through a rolling line to promote dynamic recrystallization and grain refinement during the final rolling process. Specifically: control the soaking temperature of the heating furnace to be 1210 °C, the time in the furnace to be 170 min, the initial rolling temperature to be 1080 °C, the final rolling temperature to be 915 °C, and the final rolling reduction to be 27%; the wire laying process is used to make the wire rods exiting the rolling line into wire rods through a wire laying machine. The wire rods are scattered on the roller table and conveyed along the roller table, so that the wire rods are in a high-temperature austenite state, with a relatively high quenching temperature, providing favorable conditions for forming a large supercooling degree and promoting the refinement of the lamellae of the sorbite structure and rapid nucleation. Specifically: control the wire laying temperature to be 935 °C.

[0058] The online molten salt rapid cooling isothermal treatment process uses a two-stage salt bath tank with molten salt inside. The wire rod after wire laying is transported through the first-stage salt bath tank by a roller table for pre-treatment, so that the wire rod cools down at a cooling rate of 34 °C / s, quickly skips the reticular carbide precipitation range from the high-temperature austenite state and enters the sorbite phase region, forming a structure mainly composed of sorbite with a fine lamellar spacing. Then the wire rod is transported through the second-stage salt bath tank by a roller table for post-treatment. The molten salt circulation volume in the post-treatment is appropriately reduced, the temperature is accurately controlled and the production energy consumption is reduced. The wire rod is controlled in the isothermal range and the precipitation and growth of carbides are controlled. At the same time, the sorbite structure obtained by quenching is subjected to high-temperature isothermal toughening stress relief treatment to improve the strength-plasticity matching of the wire rod. Specifically: the molten salt temperature in the pre-treatment is 573 °C, the treatment time is 30 s, the molten salt circulation volume is 570 t / h, and the molten salt temperature rise ≤ 8 °C; the molten salt temperature in the post-treatment is 566 °C, the treatment time is 185 s, the molten salt circulation volume is 215 t / h, and the molten salt temperature rise ≤ 3 °C.

[0059] In the roller table slow cooling process, the heat preservation cover is not fully closed, and the wire rod passing through the second-stage salt bath tank is transported by the conveying roller table, preventing the stress of the wire rod from increasing due to too fast cooling rate during the cooling process, and promoting the further toughening of the wire rod structure and improving the softening effect of the wire rod. Specifically: the wire rod is slowly cooled to 287 °C at a cooling rate of 0.8 °C / s; the coiling process is used to coil the wire rod into a coil by a coiling drum, and after packaging and warehousing, the finished hot-rolled wire rod is obtained, and its metallographic structure diagram is as Figure 3 shown.

[0060] Comparative Example 4:

[0061] A manufacturing method of a hot-rolled wire rod, the difference between its manufacturing method and that of Example 3 is that: the molten salt temperature in the post-treatment is 595 °C, the treatment time is 300 s, and the hot-rolled wire rod is obtained after being taken off the production line.

[0062] Comparative Example 5:

[0063] A manufacturing method of a hot-rolled wire rod, the difference between its manufacturing method and that of Example 3 is that: the molten salt temperature in the post-treatment is 515 °C, the treatment time is 100 s, and the hot-rolled wire rod is obtained after being taken off the production line. Example 4:

[0064] A preferred implementation manner of the manufacturing method of the 2400 MPa grade bridge cable hot-rolled wire rod described in the present invention, the chemical composition and mass percentage of the hot-rolled wire rod include C: 0.97%, Si: 0.9%, Mn: 0.85%, Cr: 0.61%, V: 0.055%, Mo: 0.45%, P: 0.015%, S: 0.015%, and the rest are Fe and unavoidable impurities; its manufacturing method is manufactured according to the technological process of rolling → wire laying → online molten salt rapid cooling isothermal treatment → roller table slow cooling → coiling. Specifically:

[0065] The rolling process is used to heat a billet with a specification of 220mm×220mm into a hot billet with a temperature high enough to be plastically rolled through a heating furnace, promoting the homogenization of alloy components. After the billet exits the heating furnace, it is rolled into wire rods with a diameter specification of 14mm through a rolling line, promoting dynamic recrystallization and grain refinement during the finishing rolling process. Specifically: control the soaking temperature of the heating furnace at 1240°C, the residence time in the furnace at 150 minutes, the initial rolling temperature at 1100°C, the finishing rolling temperature at 950°C, and the finishing rolling reduction at 25%; The wire laying process is used to make the wire rods exiting the rolling line into coiled bars through a wire laying machine. The coiled bars are scattered on the roller table and transported along the roller table, keeping the coiled bars in a high-temperature austenite state, with a relatively high quenching inlet temperature, providing favorable conditions for forming a large supercooling degree later, promoting the refinement of the lamellae of the sorbite structure and rapid nucleation. Specifically: control the wire laying temperature at 955°C.

[0066] The online molten salt rapid cooling and isothermal treatment process uses a two-stage salt bath tank with molten salt inside. The coiled bars after wire laying are transported through the first-stage salt bath tank by the roller table for pre-treatment, cooling the coiled bars at a cooling rate of 39°C / s, quickly skipping the reticular carbide precipitation range from the high-temperature austenite state and entering the sorbite phase region, forming a structure mainly composed of sorbite with a fine lamellar spacing. Then the coiled bars are transported through the second-stage salt bath tank by the roller table for post-treatment. The molten salt circulation volume in the post-treatment is appropriately reduced, accurately controlling the temperature and reducing production energy consumption, controlling the coiled bars in the isothermal interval and controlling the precipitation and growth of carbides. At the same time, high-temperature isothermal toughening and stress relief treatment are carried out on the sorbite structure obtained by quenching, improving the strength-plasticity matching of the coiled bars. Specifically: the molten salt temperature in the pre-treatment is 555°C, the treatment time is 25s, the molten salt circulation volume is 700t / h, and the molten salt temperature rise ≤ 8°C; the molten salt temperature in the post-treatment is 560°C, the treatment time is 250s, the molten salt circulation volume is 150t / h, and the molten salt temperature rise ≤ 3°C.

[0067] The slow cooling process of the roller table uses an incompletely closed heat preservation cover to transport the coiled bars passing through the second-stage salt bath tank by the conveying roller table, preventing the stress of the coiled bars from increasing due to too fast cooling rate during the cooling process, and promoting the further toughening of the coiled bar structure, improving the softening effect of the coiled bars. Specifically: control the coiled bars to cool slowly at a cooling rate of 0.7°C / s to 290°C; The coiling process is used to coil the coiled bars into coils through a coiling drum, and the finished hot-rolled coils are obtained after packaging and warehousing.

[0068] Comparative Example 6:

[0069] A manufacturing method of hot-rolled wire rod, the difference between its manufacturing method and that of Example 4 lies in: its manufacturing method is carried out according to the technological process of rolling → wire laying → online molten salt rapid cooling and isothermal treatment → air cooling → coiling. The air cooling is carried out by opening the heat preservation cover, controlling the wire rod to cool at a cooling rate of 1.9 °C / s to 282 °C, and obtaining the hot-rolled wire rod after being taken off the production line. The tensile strength of the hot-rolled wire rod is 1689 MPa, the reduction of area is 24%, and the difference in mechanical properties within the same coil is 56 MPa.

[0070] The hot-rolled wire rods obtained from the above Examples 1 to 4 and Comparative Examples 1 to 5 were subjected to microstructure and property tests, and the comparison results obtained are shown in Table 1 below:

[0071] Table 1. Comparison results of microstructure and properties of different hot-rolled wire rod compositions and manufacturing methods

[0072]

[0073] From the results of Examples 1 to 4, it can be seen that through the Cr-Mo-V chemical composition design combined with the online molten salt rapid cooling and isothermal technology in the present invention, the microstructure of the hot-rolled wire rod includes a mixed structure composed of tempered sorbite, ferrite and eutectoid pearlite, which can improve the strength-plasticity matching of the wire rod, reduce the fluctuation of the mechanical properties of the wire rod, and achieve a tensile strength of 1640 - 1680 MPa and a reduction of area of 27% - 32% for the product.

[0074] From the comparison results of Example 1 and Comparative Example 1, it can be seen that selecting a higher wire laying temperature is convenient for improving the strength-plasticity matching of the material with a higher quenching temperature.

[0075] From the comparison results of Example 2 and Comparative Example 2, it can be seen that the molten salt circulation amount in the front-stage treatment is greater than that in the rear-stage treatment. The higher the molten salt temperature and the shorter the treatment time in the front-stage treatment, the lower the quenching cooling rate, and the lower the energy consumption of wire rod production. However, if the molten salt temperature is too high and the treatment time is too short, it is not conducive to the rapid phase transformation of high-temperature austenite to sorbite, the interlamellar spacing of sorbite increases, the fusing difficulty increases, and the matrix strength and plasticity are affected.

[0076] From the comparison results of Example 2 and Comparative Example 3, it can be seen that the molten salt circulation amount in the front-stage treatment is greater than that in the rear-stage treatment. The lower the molten salt temperature and the longer the treatment time in the front-stage treatment, a larger supercooling degree can be formed, which promotes the full transformation of the high-temperature austenite structure into a sorbite structure with finer interlamellar spacing, provides more driving force for the dispersion precipitation of vanadium-containing carbides, and improves the matrix strength. However, if the molten salt temperature in the front-stage treatment is too low and the treatment time is too long, the holding time of the larger molten salt circulation amount increases, increasing the production energy consumption.

[0077] It can be seen from the comparison results of Example 3 and Comparative Example 4 that the higher the molten salt temperature and the longer the treatment time in the post-stage treatment, the more the lamellae are melted, the better the stress-relieving softening effect, the higher the plasticity of the wire rod. However, if the molten salt temperature is too high and the treatment time is too long, there is a risk of carbide coarsening, excessive strength loss and affecting plasticity.

[0078] It can be seen from the comparison results of Example 3 and Comparative Example 5 that the lower the molten salt temperature in the post-stage treatment, the tendency of carbide precipitation and growth can be reduced, and the precipitation of vanadium-containing carbides can be promoted. However, if the molten salt temperature is too low and the treatment time is too short, it is difficult to provide more thermal energy for isothermal toughening and stress relief, and the carbides cannot precipitate sufficiently and there is high stress in the structure, resulting in loss of strength and plasticity.

[0079] It can be seen from the comparison results of Example 4 and Comparative Example 6 that the temperature of the wire rod after online molten salt rapid cooling and isothermal treatment is relatively high. Using roller table slow cooling can prevent the stress increase caused by too fast cooling during the cooling process of the wire rod, and further promote the toughening of the wire rod structure.

[0080] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for manufacturing a 2400MPa grade hot-rolled wire rod for bridge cables, characterized in that: The manufacturing method thereof comprises: 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 include: C: 0.94%~0.97%, Si: 0.70%~0.90%, Mn: 0.85%~1.05%, Cr: 0.57%~0.67%, V: 0.040%~0.055%, Mo: 0.25%~0.45%, P≤0.015%, S≤0.015%, and the rest are Fe and unavoidable impurities; after the wire rod is spun into a wire rod at a spinning temperature of ≥930°C, it is subjected to an online molten salt rapid cooling isothermal treatment, so that the wire rod is cooled at a cooling rate of ≥32°C / s, and enters the sorbite phase region from the austenite state to form a molten steel. The hot rolled wire rod is formed into a structure mainly composed of troostite and the precipitation and growth of carbides are controlled, and isothermal toughening is performed to relieve stress. Finally, it is slowly cooled by a roller to form a hot rolled wire rod with a microstructure including a mixed structure composed of tempered troostite, ferrite and fused pearlite; the online molten salt rapid cooling isothermal treatment is divided into a front-stage treatment and a back-stage treatment, the molten salt temperature of the front-stage treatment is 555-580°C, the treatment time is 25-35s, and the molten salt circulation amount of the front-stage treatment is greater than that of the back-stage treatment; the molten salt temperature of the back-stage treatment is 560-570°C, and the treatment time is 150-250s; the roller slow cooling controls the wire rod to slowly cool to below 300°C at a cooling rate of 0.5-1°C / s.

2. The method for manufacturing the 2400MPa grade hot rolled wire rod for bridge cables according to claim 1, characterized in that: Before the rolling, the heating furnace is controlled to have a soaking temperature of 1180-1240° C. and the time in the furnace is ≥150 min.

3. The method for manufacturing the 2400MPa grade hot rolled wire rod for bridge cables according to claim 1, characterized in that: During the rolling, the initial rolling temperature is controlled to be 1060-1100° C., the final rolling temperature is controlled to be 900-950° C., and the final rolling reduction is controlled to be 23%-29%.

4. The method for manufacturing the 2400MPa grade hot rolled wire rod for bridge cables according to claim 1, characterized in that: The molten salt circulation volume of the front-end treatment is 500-700 t / h, and the molten salt temperature rise is ≤8°C; the molten salt circulation volume of the back-end treatment is 150-250 t / h, and the molten salt temperature rise is ≤3°C.

5. A 2400MPa grade hot-rolled wire rod for bridge cables, characterized in that: The hot-rolled wire rod is manufactured by the method for manufacturing 2400MPa-grade hot-rolled wire rod for bridge cables according to any one of claims 1 to 4.

6. The 2400MPa grade hot rolled wire rod for bridge cables according to claim 5, characterized in that: The interlamellar spacing of the tempered troostite is 70-100 nm, and the volume percentage of the tempered troostite and the fused pearlite is ≥94%.

7. The 2400MPa grade hot rolled wire rod for bridge cables according to claim 5, characterized in that: The network carbide grade of the hot-rolled wire rod is grade 0, and the mechanical property difference is ≤45MPa.

8. The 2400MPa grade hot rolled wire rod for bridge cables according to claim 5, characterized in that: The hot-rolled wire rod has a diameter of 10.0-16.0 mm, a tensile strength of 1640-1680 MPa, and a cross-sectional shrinkage of 27%-32%.

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