A 2060MPa grade hot-rolled wire rod for bridge cables and a manufacturing method thereof

Abstract

The invention relates to a hot-rolled wire rod for 2060MPa-level bridge cables and a manufacturing method thereof. After rolling and spinning into a wire rod with C-Si-Mn-Cr-V-Nb components, the wire rod is subjected to an online molten salt strong isothermal treatment to cool the wire rod at a cooling rate of ≥34°C / s, enter a sorbite phase region from an austenite state, form a structure dominated by sorbite with fine lamellar spacing, and isothermally treated to promote carbide spheroidization. Finally, the hot-rolled wire rod is subjected to roller slow cooling to form a microstructure dominated by tempered sorbite and the rest being a mixed structure composed of ferrite and micro-spheroidized carbides. The hot-rolled wire rod can effectively control the deteriorated structure affecting the performance of the finished wire rod product in the production process, realize stable production, improve the strength-plasticity matching of the wire rod, reach a tensile strength of 1440-1490MPa, and a cross-sectional shrinkage of 42%-46%. The wire rod is suitable for efficient and stable production of 2060MPa-level bridge cables.

Description

Technical Field

[0001] The invention belongs to the technical field of hot-rolled wire rods, and in particular relates to a 2060MPa-grade hot-rolled wire rod for bridge cables and a manufacturing method thereof. Background Art

[0002] With the increase of bridge span, the strength level of bridge cables used is constantly improving. Bridge cables are made of hot-rolled wire rods through processes such as wire laying, pickling, multi-pass drawing, hot-dip galvanizing, and stranding. In order to meet the strength level of steel wire and drawing and torsion performance, 2060MPa-grade bridge cables have extremely strict requirements on the parent material hot-rolled wire rods. Since the existing hot-rolled wire rods for bridge cables usually use the Stelmor air-cooled line to control the hot-rolled wire rod structure, but the extremely high C content and alloy content of the wire rods for 2060MPa-grade bridge cables will cause the wire rods to be extremely difficult to control during the production process. The deterioration of the structure, such as net carbon and martensite, which affects the performance of the finished wire rods, will lead to a high risk of wire breakage during the wire drawing process, and it is difficult for steel mills to produce stably. Therefore, it is an urgent problem to develop a 2060MPa-grade bridge cable hot-rolled wire rod with better drawing and torsion performance and stable production to meet the development of the steel industry and market demand.

[0003] The technical difficulties and causes of the existing hot-rolled wire rods for bridge cables being difficult to meet production and performance requirements include:

[0004] 1. As an economical and effective carbide strengthening element and austenite forming element, the C element has a high content in 2060MPa grade bridge cable wire rod, but it also aggravates the carbon center segregation during the solidification process of the billet. It is more likely to precipitate along the grain boundary due to the long precipitation temperature interval of the secondary cementite during the controlled cooling process of the Stelmor air-cooled wire after rolling, forming a network carbide. Even after the Stelmor wire is treated with strong air cooling, the network carbide still has a high level, which seriously affects the uniformity of the wire rod structure, increases the brittleness of the wire rod, and causes a significant decrease in plasticity, thereby aggravating the risk of wire breakage in the wire drawing process. For this reason, although patent CN114657471B proposes a production method for wire rods of ≥2060MPa grade bridge cables, adopts a C-Si-Mn-Cr-B composition design, combines controlled rolling and spinning with Stelmor air cooling + mist cooling to further improve the cooling temperature before phase transformation. The cooling rate is increased to improve the network carbide, but on the one hand, it is limited by the maximum cooling capacity and the improvement of the network carbide is limited. On the other hand, in order to improve the strength of the wire rod, a large amount of Si, Mn or Cr elements are added to the wire rod to obtain a higher troostitization rate and fine cementite lamella spacing, but the addition of hardenability alloying elements also increases the segregation tendency. In the process of increasing the wind cooling intensity or mist cooling or water bath cooling, the uncontrollability of the air volume and air temperature is further increased. When water and the wire rod are exchanged for heat, more bubbles will be generated and attached to the surface of the wire rod, affecting heat transfer, which will lead to unstable wire rod cooling rate control. Affected by segregation, some overcooling positions are prone to form hard and brittle bainite or martensite structures that are unfavorable for drawing, affecting the uniformity of the organization and the plasticity of the wire rod. The fluctuation of mechanical properties increases sharply, which is easy to cause brittle fracture in the wire rod winding process or cracking in the subsequent drawing and torsion process, which is not conducive to stable production.

[0005] Second, in order to improve the strength of the wire rod, the temperature will be lowered during rolling and spinning, in order to refine the austenite grains at a low temperature and a large amount, combined with increasing the content of hardenability elements and the air cooling strength after spinning, to promote the formation of refined pearlite, i.e., sorbite. However, it also increases the deformation resistance of the rolled piece during the rolling process, intensifies the wear of the rolling line, and slows down the rolling speed. At the same time, the risk of precipitation of abnormal low-temperature structures increases, and the uniformity of the structure decreases. In addition, due to the limitations of continuous cooling and minimum cooling capacity, the time for the wire rod to pass through the phase transformation temperature range is relatively short, which will limit the increase in the sorbite content. After the phase transformation is incubated, there is a high stress in the sorbitized structure. Strengthening elements such as Cr limit the improvement of the plasticity of the wire rod, which will lead to insufficient uniformity and plasticity of the structure, causing wire breakage or torsion failure during drawing. For this reason, although, for example, patent CN112391584A In the high-strength wire rod for bridge cables disclosed in CN107299280B, etc., the heating after Stelmor's fast-then-slow organization regulation and isothermal salt bath offline heat treatment are further combined to improve the organization uniformity and plasticity. However, it will also lead to an increase in the process, production time and cost. The steel mill's coiling or transportation process is affected by abnormal organization, which is not conducive to stable production. The steel mill or downstream users still need to re-unwind and heat treat, which is not conducive to efficient production and cost control.

[0006] 3. In order to further improve the strength of hot-rolled wire rods for bridge cables, although trace strengthening elements such as V, Nb, Ti, and B are added to the wire rods, the low-temperature rolling and continuous cooling phase transformation control restrictions of the Stelmor air-cooled line will lead to coarsening of precipitation or a small amount of precipitation, limiting the strengthening effect of micro-alloy elements, and excessive addition will cause excessive increase in wire rod costs. Summary of the invention

[0007] The present invention aims to solve at least one of the above-mentioned technical problems to a certain extent. The present invention provides a 2060MPa grade hot-rolled wire rod for bridge cables and a manufacturing method thereof, which can effectively control the deteriorated structure that affects the performance of the wire rod finished product during the production process, improve the strength and plasticity matching of the wire rod, and is suitable for the efficient and stable production of 2060MPa grade bridge cables.

[0008] The technical solution adopted by the present invention to solve its technical problem is:

[0009] A method for manufacturing a 2060MPa grade hot-rolled wire rod for bridge cables, the manufacturing method comprising:

[0010] The hot rolled wire rod is rolled to produce a wire rod according to its chemical composition, wherein the chemical composition and mass percentage of the hot rolled wire rod include: C: 0.87% to 0.91%, Si: 0.70% to 0.85%, Mn: 0.72% to 0.90%, Cr: 0.25% to 0.45%, V: 0.02% to 0.03%, Nb: 0.015% to 0.025%, P≤0.015%, S≤0.015%, and the rest are Fe and Impurities can be avoided; after the wire rod is spun into a wire rod at a spinning temperature of ≥910°C, it is subjected to an online molten salt strong isothermal treatment, so that the wire rod is cooled at a cooling rate of ≥34°C / s, entering the sorbite phase region from the austenite state, forming a structure mainly composed of sorbite with fine lamellar spacing and isothermally treated to promote carbide spheroidization, and finally slowly cooled by a roller to form a hot-rolled wire rod with a microstructure mainly composed of tempered sorbite and the rest being a mixed structure composed of ferrite and micro-spheroidized carbides.

[0011] The design basis of the chemical composition and mass percentage of the above hot rolled wire rod includes:

[0012] (1) Carbon: As an effective carbide strengthening element and austenite forming element, C is cheaper than other alloying elements. As the carbon content increases, it is beneficial to form more cementite lamellae in the wire rod during the controlled cooling process, thereby improving the tensile strength of the material. However, as the carbon content in hypereutectoid steel increases, it will promote the central carbon segregation during the solidification process of the billet, increase the tendency of decarburization and precipitation of network cementite, deteriorate the toughness and plasticity of the material, and lead to the wire rod cross-sectional shrinkage, drawing and torsion indicators being unqualified. Therefore, in order to take into account the high strength requirements of 2060MPa grade bridge cables, regulate the peak precipitation temperature of troostite, and reduce the difficulty of controlling network carbides, the mass percentage of C is controlled to be 0.87%~0.91%.

[0013] (2) Silicon: The Si element is often used as a deoxidizer during the smelting process. The Si dissolved in the ferrite phase will play a role in strengthening the material. At the same time, it can inhibit the coarsening of cementite, so that a finer troostite structure can be obtained during the online molten salt strong isothermal treatment. It also accelerates the diffusion rate of carbon, which is beneficial to reduce the difficulty of isothermal tempering and softening of troostite. After the wire rod is drawn into steel wire, it can reduce the strength loss in the subsequent hot-dip galvanizing process. However, too high a silicon content will make the steel easier to decarburize when heated at high temperature, prolong the transformation time during the phase change process, and reduce the toughness of the steel. Therefore, the mass percentage of Si is controlled to be 0.70%~0.85%.

[0014] (3) Manganese: Mn can be added as a deoxidizer during the smelting process, mainly playing a role in solid solution strengthening, while increasing the hardenability of the wire rod and the stability of austenite, reducing the phase transformation temperature, and thus promoting the rapid nucleation of the troostite structure with fine lamellar spacing and the dispersion and precipitation of V-containing carbides during the online molten salt strong isothermal treatment, thereby improving the matrix strength. However, when the Mn content is too high, it will increase the overheating sensitivity of the steel, grain coarsening and component segregation tendency, and increase the risk of low-temperature microstructure precipitation in the core of the wire rod. At the same time, it will reduce the diffusion activity of carbon, which is not conducive to promoting the tempering softening of the structure, thereby losing the plasticity of the wire rod. Therefore, in order to take into account the high strength and plasticity and microstructure uniformity of the hot-rolled wire rod, the mass percentage of Mn is controlled to be 0.72%~0.90%.

[0015] (4) Chromium: Cr is a medium-strong carbide-forming element in high carbon steel. It can improve the stability of austenite and the hardenability of wire rod, shift the C curve of steel to the right, and refine the spacing between sorbite lamellae, improve the drawing performance and increase the matrix strength. At the same time, it can reduce the strength loss during the subsequent hot-dip galvanizing process of steel wire. However, too high Cr content will aggravate component segregation, increase the risk of abnormal tissue precipitation, reduce the activity of carbon in steel, and significantly increase the difficulty of improving the plasticity of wire rod. It is not conducive to isothermal softening during online molten salt strong isothermal treatment and will deteriorate the torsional performance of steel wire. Therefore, the mass percentage of Cr is controlled to be 0.25%~0.45%.

[0016] (5) Vanadium: As a strong carbide-forming element, V can be dispersed and precipitated in large quantities in the medium temperature range of 500~600℃, which can play a role in strengthening precipitation, increase the strength of the matrix, and provide hydrogen traps to improve the hydrogen embrittlement resistance of the wire rod. However, due to the high price of V, excessive addition will lead to an increase in the cost of the wire rod and increase the risk of coarsening during online molten salt strong isothermal treatment, thereby losing the toughness of the steel. Therefore, the mass percentage of V is controlled to be 0.02%~0.03%.

[0017] (6) Niobium: As a grain-refining strengthening element, Nb has a higher solution temperature than V. It can induce precipitation and pin grain boundaries through high-temperature rolling strain, thereby inhibiting grain growth and refining grains. It can also further strengthen the steel by precipitating in ferrite. However, since Nb is expensive, excessive addition will increase the cost of the wire rod and reduce the incremental strengthening. Therefore, the mass percentage of Nb is controlled to be 0.015%~0.025%.

[0018] (7) Phosphorus and sulfur: P and S are impurity elements. The lower the better. Therefore, P is controlled to be ≤ 0.015% and S is ≤ 0.015%.

[0019] The hot-rolled wire rod is designed with C-Si-Mn-Cr-V-Nb composition containing trace V and Nb elements, and the Cr content is relatively small, which can regulate the segregation effect, hardenability and peak precipitation temperature of sorbite of the wire rod, and provide favorable conditions for controlling the network carbides and low-temperature abnormal organization during the online molten salt strong isothermal treatment, promoting the sorbite phase transformation and lamellar refinement, promoting the dispersion precipitation of vanadium-containing carbides, and reducing the difficulty of isothermal softening. On this basis, the selection of a higher wire-spinning temperature can reduce the restriction on the rolling temperature, so as to promote the precipitation phase of Nb element to pin the grain boundary and refine the grains, inhibit the growth of austenite grains, and avoid the formation of network cementite in the wire-spinning stage, which provides favorable conditions for controlling the network carbides and sorbite phase transformation. After wire-spinning, air cooling is not used but direct online molten salt strong isothermal treatment is used:

[0020] 1. Compared with the existing Stelmor air-cooling line or the treatment process combined with water mist, the maximum cooling capacity is limited. The above manufacturing method can utilize the high heat exchange capacity of molten salt to promote rapid cooling of wire rod. On the one hand, the faster cooling rate makes the wire rod pass through the secondary cementite precipitation temperature range of 700~800℃ for only a few seconds, making it difficult to form secondary cementite and thus inhibiting the formation of network carbides, effectively reducing the level of network carbides, and avoiding the adverse effects of network carbides on organizational uniformity, mechanical properties, and especially the plasticity and toughness of wire rod; on the other hand, the faster cooling rate makes the wire rod quickly enter the troostite phase region from the high-temperature austenite state, forming a larger temperature gradient. The larger supercooling can promote the nucleation of troostite and reduce the thickness of cementite lamellae, which is beneficial to improving the strengthening effect of carbon element and the drawing performance of wire rod, and reducing the difficulty of troostite softening and carbide spheroidization transformation.

[0021] 2. Compared with the existing Stelmor strong wind cooling or combined with water mist or water bath treatment process, the controlled cooling is unstable. Since the molten salt can cover the surface of the wire rod for faster and more uniform heat exchange when the wire rod passes through the molten salt, there is no temperature difference between the windward side and the leeward side, and there is no problem of bubble attachment caused by water heat exchange affecting heat transfer. The temperature difference between each position of the same circle of the wire rod and the upper edge to the core of the cross section can be effectively reduced. On the one hand, the formed troostite is mainly composed of fine lamellar spacing, and the troostite content is more evenly distributed, which can avoid the wire rod from being overcooled into the bainite or martensite phase region and producing low-temperature brittle abnormal tissue; on the other hand, the wire rod can be consistent with the molten salt temperature, and a longer phase transformation incubation time can be carried out at the troostite peak precipitation temperature, which promotes the full phase transformation of the troostite, avoids austenite residues and then produces abnormal tissue in the subsequent roller slow cooling, thereby effectively improving the uniformity of the tissue, avoiding abnormal bainite and martensite tissues, making the wire rod winding and transportation and downstream silk-making and torsion processes less prone to brittle fracture, and the production and product performance are more stable.

[0022] 3. Compared with the existing Stelmor slow air cooling, insulation or combined water mist treatment process with limited minimum cooling capacity and continuous cooling treatment, the online molten salt strong isothermal treatment can make the wire rod consistent with the molten salt temperature, and carry out more stable and longer isothermal treatment in the sorbite phase region. On the one hand, the extended phase transformation time makes the sorbite fully inoculated and in the dispersion precipitation range of vanadium-containing carbides, which can give full play to the strengthening effect of trace V elements and improve the matrix strength. On the other hand, the temperature of the sorbite phase region is higher than that of the bainite phase region, and the high temperature state is maintained for a longer time. With the end of the phase transformation, the wire rod can enter the high-temperature isothermal region, providing more thermal power, promoting the strengthening isotherm of the wire rod structure, and promoting the transformation of carbides to spheroidized structure, so as to reduce the organizational stress and dislocation density, and improve the strength-plasticity matching of the wire rod. After that, when the roller is slowly cooled, the cooling rate can be reduced to prevent the stress of the wire rod from increasing during the cooling process, and the wire rod structure can be further toughened, the softening effect of the wire rod can be improved, and the wire rod structure can be controlled. At the same time, compared with offline processing, there are fewer processes, lower costs, and higher production efficiency.

[0023] Due to the high content of alloy elements in the composition system, selecting a suitable heating furnace soaking temperature before rolling can promote uniform diffusion of components, reduce the impact of segregation, and avoid the risk of burning and decarburization caused by too long time in the furnace. In a preferred embodiment, before rolling, the heating furnace soaking temperature is controlled to be 1120~1170℃, and the time in the furnace is 120~220min.

[0024] Due to the high spinning temperature, the rolling temperature can be appropriately increased to reduce the deformation resistance of the rolled piece and the wear on the rolling mill. At the same time, the reduction amount can be controlled to promote the pinning of the grain boundary with the help of the Nb element precipitation phase, avoid the aggregation and growth of the precipitation phase, and promote dynamic recrystallization, grain refinement, and matrix toughening during the final rolling process. In a preferred embodiment, during the rolling, the initial rolling temperature is controlled to be 1070~1100℃, the final rolling temperature is 930~980℃, and the final rolling reduction is 25%~31%.

[0025] The lower the molten salt temperature of the online molten salt strong isothermal treatment, the faster the wire rod can be cooled, the network carbides can be controlled, and the nucleation and lamella refinement of sorbite can be promoted, and more driving force can be provided for the large-scale dispersion and precipitation of V-containing carbides in the crystal, thereby improving the matrix strength. However, if the molten salt temperature is too low, there is a risk of abnormal bainite structure and even difficulty in precipitating V-containing precipitation phases. At the same time, it is not conducive to the isothermal transformation of organizational strengthening and carbide spheroidization, which will cause strength or plasticity loss. On the contrary, the higher the molten salt temperature, the larger the sorbite lamella spacing will be, and more thermal power can be provided for organizational softening, so that the strength of the wire rod decreases and the plasticity increases. However, if the molten salt temperature is too high, the cooling rate of the wire rod decreases, which is not conducive to controlling the network carbides and reducing the sorbite lamella spacing. At the same time, too high a temperature will cause carbide precipitation. The risk of coarsening and loss of strength and toughness; the longer the treatment time, the more complete the transformation of austenite to troostite, the better the softening effect, the stress of the wire rod decreases and the plasticity increases, but if the treatment time is too long, there is a risk of precipitation phase or carbide aggregation and growth and loss of strength and plasticity, which will also cause an increase in production energy consumption; conversely, the shorter the treatment time, the lower the strengthening isothermal effect and the plasticity of the wire rod, but if the treatment time is too short, it will affect the troostite phase transformation, the organization strengthening isothermal or the large amount of precipitation phases such as V and Cr, and will lose strength and plasticity. Therefore, the molten salt temperature and treatment time can be further controlled to improve the strength-plasticity matching of the wire rod. In a preferred embodiment, the molten salt temperature of the online molten salt strong isothermal treatment is 545~590℃, and the treatment time is 400~550s.

[0026] Since the temperature gradient of the wire rod from the high-temperature austenite to the troostite phase is relatively large, selecting an appropriate molten salt circulation rate to control the molten salt temperature rise can improve the processing accuracy and promote the formation of troostite with mainly fine lamellar spacing. In a preferred embodiment, the molten salt circulation rate of the online molten salt strong isothermal treatment is 520~620t / h, and the molten salt temperature rise is ≤10℃.

[0027] The roller slow cooling controls the wire rod to cool down at a lower cooling rate, which is beneficial to further toughening the wire rod structure and improving the softening efficiency, while avoiding the cooling rate being too low and affecting the wire rod production efficiency. In a preferred embodiment, the roller slow cooling controls the wire rod to cool down slowly at a cooling rate of 0.2~0.4℃ / s above 300℃.

[0028] In a preferred embodiment, the roller slow cooling adopts an open insulation cover, and the wire rod is transported by the roller into the insulation cover to control the cooling of the wire rod. After the wire rod comes out of the salt bath at 550-590°C, it can slowly cool down by its own waste heat, further reducing energy consumption.

[0029] A 2060MPa grade hot-rolled wire rod for bridge cables, the hot-rolled wire rod is manufactured by any one of the above-mentioned methods for manufacturing 2060MPa grade hot-rolled wire rod for bridge cables.

[0030] The above-mentioned hot-rolled wire rod adopts a hypereutectoid component system with composite addition of Nb and V, and is combined with organizational control to form a mixed organization composed mainly of tempered troostite and a small amount of ferrite and micro-spheroidized carbide. The interlamellar spacing of troostite is finer than that of pearlite, and the strength and drawing hardening ability are higher than those of pearlite. After the isothermal transformation to tempered troostite, the strength characteristics can be retained to obtain a toughened organizational state, and the proportion of ferrite organization can be reduced. Combined with the strengthening effect of Nb and V, a high material strength is maintained. At the same time, the carbide is transformed into a spheroidized organization and is evenly distributed on the plastic matrix, which can regulate the plasticity of the wire rod to achieve high strength and plasticity matching. At the same time, by controlling the formation of deteriorated organizations such as network carbides, bainite, martensite, etc. that affect the performance of the finished wire rod, the tempered troostite content is regulated to be evenly distributed, and the organizational uniformity is further improved, which is more convenient for stable production of steel mills and downstream users.

[0031] The lower the proportion of the tempered troostite, the lower the matrix strength and drawing properties. In a preferred embodiment, the volume percentage of the tempered troostite is ≥90%.

[0032] The finer the lamellar spacing of the tempered troostite, the higher the matrix strength and the drawing hardening ability. However, if it is too fine, the required molten salt temperature will decrease, which is not conducive to controlling production energy consumption and strengthening the isothermal effect. In a preferred embodiment, the lamellar spacing of the tempered troostite is 75~120mm.

[0033] In a preferred embodiment, the network carbide level of the hot-rolled wire rod is level 0, which can effectively improve the strengthening effect of carbon element, organizational uniformity and overall plasticity.

[0034] Since the network carbides and deteriorated tissues are effectively controlled, the wire rod tissue is uniform, and the fluctuation of mechanical properties is correspondingly reduced. In a preferred embodiment, the mechanical property difference of the hot-rolled wire rod is ≤50MPa.

[0035] In a preferred embodiment, the diameter of the hot-rolled wire rod is 12.0~15.0mm, the tensile strength is 1440~1490MPa, and the cross-sectional shrinkage rate is 42%~46%. The higher tensile strength and cross-sectional shrinkage rate make the wire rod exhibit better strength and toughness, which is beneficial to reduce the risk of wire breakage and torsional cracking during deep drawing, so that the strength grade of the bridge cable reaches 2060MPa and can be produced stably.

[0036] Compared with the prior art, the beneficial effects of the present invention are at least:

[0037] (1) Aiming at the current situation that it is extremely difficult to control the deterioration structure that affects the performance of the finished wire rod in the production method of 2060MPa grade hot-rolled wire rod for bridge cables, resulting in a high risk of wire breakage during the wire drawing process and difficulty in stable production in steel mills, the manufacturing method of the present invention controls the wire rod to quickly pass through the network carbide precipitation zone from the high-temperature austenite state to the sorbite phase zone through the C-Si-Mn-Cr-Nb-V chemical composition design and the online molten salt strong isothermal technology, forming a structure dominated by sorbite with fine lamellar spacing. At the end, the wire rod enters the high temperature isothermal zone, which promotes the wire rod structure to be strengthened isothermally, improves the strength-plasticity matching of the wire rod, and avoids the formation of bainite or martensite. Then, the slow cooling by the roller promotes further toughening of the wire rod structure, which can effectively control the deterioration of the structure that affects the performance of the wire rod product during the production process, improve the strengthening effect of carbon elements, give full play to the strengthening effect of Nb and V, and improve the strength-plasticity matching of the wire rod. At the same time, compared with offline salt bath treatment, it can reduce the process, cost and time consumption, which is beneficial to the stable production of steel mills and downstream users, and has good industrial adaptability.

[0038] (2) Aiming at the current situation that the deterioration of the hot-rolled wire rod for 2060MPa bridge cables is difficult to control, and the uniformity and plasticity of the structure are insufficient, the hot-rolled wire rod of the present invention is a mixed structure composed mainly of tempered troostite and a small amount of ferrite and micro-spheroidized carbide. The troostite interlamellar spacing is refined to promote the full transformation and distribution of the troostite structure, and the strength characteristics are retained after isothermal transformation to tempered troostite, the proportion of ferrite structure is reduced, and the high material strength is maintained by combining the strengthening effect of Nb and V. At the same time, the isothermal toughening softening structure is strengthened and the transformation of carbide to spheroidized structure is promoted. , effectively improve the plasticity of wire rod, can achieve a tensile strength of 1440~1490MPa, and a cross-sectional shrinkage rate of 42%~46%. At the same time, it avoids the deterioration of the structure of mesh carbon, martensite, etc. that affects the performance of the finished wire rod. The organization has better uniformity, which can avoid brittle fracture during the coiling and transportation process of the steel plant, and ensure stable production of hot-rolled wire rods. At the same time, it regulates the matching of high strength and plasticity of the wire rod, and is used in fields such as 2060MPa-level bridge cables. It is beneficial to reduce the risk of wire breakage in the wire drawing and torsion process, so that the product quality is stable and downstream users can produce efficiently and stably, and it has good market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0040] Figure 1 is a metallographic structure diagram of Example 1 of the present invention;

[0041] Figure 2 is the metallographic structure diagram of Example 2 of the present invention;

[0042] Figure 3 It is the metallographic structure diagram of Example 3 of the present invention. DETAILED DESCRIPTION

[0043] The embodiments described below with reference to the accompanying drawings are exemplary and are only for illustration and do not limit the description of the features and characteristics of the present invention, so as to propose the best way to implement the present invention, and are intended to be used to explain the present invention and are sufficient to enable those skilled in the art to implement the present invention, but cannot be understood as any limitation on the scope of the present invention, which is limited only by the appended claims; the organization and performance testing of the hot-rolled wire rods obtained in the following embodiments and comparative examples include: the tensile test is carried out using "GB-T 228.1-2021 Metallic Material Tensile Test Part 1: Room Temperature Test Method" to obtain the tensile strength and cross-sectional reduction rate; the organization test is carried out according to the metal microstructure detection method of GB / T13298 standard; the mechanical property same circle difference test method: take 2 circles of wire rod 5m away from the end of the coil, take the overlap area position as the base point, divide each circle of wire rod into 8 sections on average, take 1 tensile specimen on each section, and the strength extreme difference of the tensile specimen after the tensile test is the mechanical property same circle difference. Embodiment 1:

[0044] A preferred embodiment of the manufacturing method of the 2060MPa grade hot-rolled wire rod for bridge cables of the present invention, the chemical composition and mass percentage of the hot-rolled wire rod include C: 0.87%, Si: 0.77%, Mn: 0.84%, Cr: 0.28%, V: 0.022%, Nb: 0.024%, P: 0.015%, S: 0.015%, and the rest are Fe and unavoidable impurities; the manufacturing method thereof is manufactured according to the process flow of rolling → spinning → online molten salt strong isothermal treatment → roller slow cooling → coiling, specifically:

[0045] The rolling process is used to heat a steel billet with a specification of 220mm×220mm through a heating furnace to obtain a high-temperature steel billet that can be rolled into plasticity, control the parameters of the heating furnace to promote uniform diffusion of components in the steel billet, reduce segregation and control decarburization, and after the steel billet leaves the heating furnace, roll the steel billet into a wire with a diameter of 13mm through a rolling line, select a suitable rolling temperature and deformation, and use the Nb element precipitation phase to pin the grain boundary to promote dynamic recrystallization and refine the grains during the final rolling process. Specifically: control the heating furnace soaking temperature to 1170°C, and when the furnace is The time interval is 120min, the initial rolling temperature is 1100℃, the final rolling temperature is 980℃, and the final rolling reduction is 29%; the wire-spinning process is used to convert the wire rods coming out of the rolling line into wire rods through a wire-spinning mechanism, and the wire rods are spread on the rollers and transported along the rollers. An appropriate wire-spinning temperature is selected to promote the wire rods to be in a high-temperature austenite state, and to avoid the formation of network carbides in the wire-spinning stage caused by too low a wire-spinning temperature, so as to form a large temperature gradient later, thereby providing favorable conditions for promoting the troostite phase transformation dominated by fine lamellar spacing. Specifically, the wire-spinning temperature is controlled to be 940℃.

[0046] The online molten salt strong isothermal treatment process adopts a salt bath tank with molten salt inside. The wire rod after spinning is conveyed through the salt bath tank by rollers, so that the wire rod is cooled at a cooling rate of 35°C / s, and quickly passes through the network carbide precipitation interval from the high-temperature austenite state and enters the sorbite phase area, inhibiting the formation of network carbides, promoting the phase transformation of high-temperature austenite to sorbite, forming a structure dominated by sorbite with fine lamellar spacing, and promoting the large-scale dispersion and precipitation of vanadium-containing carbides. As the phase transformation ends, the wire rod enters the high-temperature isothermal interval, promoting the wire rod structure to undergo enhanced isothermal treatment, promoting the transformation of carbides to spheroidized structures, and improving the strength and plasticity matching of the wire rod. Specifically: the molten salt temperature of the online molten salt strong isothermal treatment is 590°C, the treatment time is 550s, the molten salt circulation volume is 560t / h, and the molten salt temperature rise is ≤10°C.

[0047] The roller slow cooling process adopts an open insulation cover, and the conveyor roller conveys the wire rod passing through the salt bath tank into the insulation cover to prevent the wire rod from increasing stress during the cooling process, and promotes further toughening of the wire rod structure, thereby improving the softening effect of the wire rod. Specifically: the wire rod is controlled to be slowly cooled at a cooling rate of 0.4°C / s above 300°C; 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. Its metallographic structure diagram is as follows Figure 1 shown.

[0048] Comparative Example 1:

[0049] A method for manufacturing a hot-rolled wire rod, the manufacturing method of which is different from that of Example 1 in that: the manufacturing method is manufactured according to the process flow of rolling → spinning → Stelmor air cooling, specifically: the heating furnace soaking temperature is controlled to be 1090°C, the furnace time is 240min, the initial rolling temperature is 1035°C, the final rolling temperature is 895°C, and the spinning temperature is 875°C; the Stelmor strong air cooling adopts an air volume of 260,000 m per fan 3 / h, open 1~5# fans at 95%, cool the wire rod to 680℃ at a cooling rate of 9.1℃ / s, and then open 6~14# fans at 35%, cool the wire rod to 290℃ at a cooling rate of 4.1℃ / s, and obtain the hot-rolled wire rod product after it comes off the line.

[0050] Comparative Example 2:

[0051] A method for manufacturing a hot-rolled wire rod, which differs from Example 1 in that: the heating furnace soaking temperature is controlled to be 1100°C, the furnace time is 200 min, the initial rolling temperature is 1055°C, the final rolling temperature is 915°C, the spinning temperature is 895°C, and the online molten salt intensive isothermal treatment process causes the wire rod to cool at a cooling rate of 30°C / s, and a hot-rolled wire rod finished product is obtained after it comes off the line. Embodiment 2:

[0052] A preferred embodiment of the manufacturing method of the 2060MPa grade hot-rolled wire rod for bridge cables of the present invention, the chemical composition and mass percentage of the hot-rolled wire rod include C: 0.88%, Si: 0.85%, Mn: 0.75%, Cr: 0.25%, V: 0.02%, Nb: 0.015%, P: 0.012%, S: 0.015%, and the rest is Fe and unavoidable impurities; the manufacturing method is manufactured according to the process flow of rolling → spinning → online molten salt strong isothermal treatment → roller slow cooling → coiling, specifically:

[0053] The rolling process is used to heat a steel billet with a specification of 220mm×220mm through a heating furnace to obtain a high-temperature steel billet that can be rolled into plasticity, control the parameters of the heating furnace to promote uniform diffusion of components in the steel billet, reduce segregation and control decarburization, and after the steel billet leaves the heating furnace, roll the steel billet into a wire with a diameter of 12mm through a rolling line, select a suitable rolling temperature and deformation, and use the Nb element precipitation phase to pin the grain boundary to promote dynamic recrystallization and refine the grains during the final rolling process. Specifically: control the heating furnace soaking temperature to 1155°C, and when the furnace is The time interval is 150min, the initial rolling temperature is 1085℃, the final rolling temperature is 955℃, and the final rolling reduction is 31%; the wire-spinning process is used to convert the wire rods coming out of the rolling line into wire rods through a wire-spinning mechanism, and the wire rods are spread on the rollers and transported along the rollers. An appropriate wire-spinning temperature is selected to promote the wire rods to be in a high-temperature austenite state, and to avoid the formation of network carbides in the wire-spinning stage caused by too low a wire-spinning temperature, so as to form a large temperature gradient later, thereby providing favorable conditions for promoting the troostite phase transformation dominated by fine lamellar spacing. Specifically, the wire-spinning temperature is controlled to be 925℃.

[0054] The online molten salt strong isothermal treatment process adopts a salt bath tank with molten salt inside. The wire rod after spinning is conveyed through the salt bath tank by rollers, so that the wire rod is cooled at a cooling rate of 36°C / s, and quickly passes through the network carbide precipitation interval from the high-temperature austenite state and enters the sorbite phase area, inhibiting the formation of network carbides, promoting the phase transformation of high-temperature austenite to sorbite, forming a structure dominated by sorbite with fine lamellar spacing, and promoting the large-scale dispersion and precipitation of vanadium-containing carbides. As the phase transformation ends, the wire rod enters the high-temperature isothermal interval, promoting the wire rod structure to undergo enhanced isothermal treatment, promoting the transformation of carbides to spheroidized structures, and improving the strength and plasticity matching of the wire rod. Specifically: the molten salt temperature of the online molten salt strong isothermal treatment is 557°C, the treatment time is 525s, the molten salt circulation volume is 585t / h, and the molten salt temperature rise is ≤10°C.

[0055] The roller slow cooling process adopts an open insulation cover, and the conveyor roller conveys the wire rod passing through the salt bath tank into the insulation cover to prevent the wire rod from increasing stress during the cooling process, and promotes further toughening of the wire rod structure, thereby improving the softening effect of the wire rod. Specifically: the wire rod is controlled to be slowly cooled at a cooling rate of 0.26°C / s above 300°C; 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. Its metallographic structure diagram is as follows Figure 2 shown.

[0056] Comparative Example 3:

[0057] A method for manufacturing a hot-rolled wire rod, the manufacturing method of which is different from that of Example 2 in that the molten salt temperature of the online molten salt intensive isothermal treatment is 600° C., and a hot-rolled wire rod finished product is obtained after the production line is off-line.

[0058] Comparative Example 4:

[0059] A method for manufacturing a hot-rolled wire rod, the manufacturing method of which is different from that of Example 2 in that the molten salt temperature of the online molten salt intensive isothermal treatment is 520°C, and a hot-rolled wire rod finished product is obtained after the production line is off-line. Embodiment 3:

[0060] A preferred embodiment of the manufacturing method of the 2060MPa grade hot-rolled wire rod for bridge cables of the present invention, the chemical composition and mass percentage of the hot-rolled wire rod include C: 0.91%, Si: 0.79%, Mn: 0.72%, Cr: 0.39%, V: 0.03%, Nb: 0.018%, P: 0.015%, S: 0.013%, and the rest are Fe and unavoidable impurities; the manufacturing method thereof is manufactured according to the process flow of rolling → spinning → online molten salt strong isothermal treatment → roller slow cooling → coiling, specifically:

[0061] The rolling process is used to heat a steel billet with a specification of 220mm×220mm through a heating furnace to obtain a high-temperature steel billet that can be rolled into plasticity, control the parameters of the heating furnace to promote uniform diffusion of components in the steel billet, reduce segregation and control decarburization, and after the steel billet leaves the heating furnace, roll the steel billet into a wire with a diameter of 14mm through a rolling line, select a suitable rolling temperature and deformation, and use the Nb element precipitation phase to pin the grain boundary to promote dynamic recrystallization and refine the grains during the final rolling process. Specifically: control the heating furnace soaking temperature to 1120°C, and when the furnace is The time interval is 220min, the initial rolling temperature is 1070℃, the final rolling temperature is 930℃, and the final rolling reduction is 26%; the wire-spinning process is used to convert the wire rods coming out of the rolling line into wire rods through a wire-spinning mechanism, and the wire rods are spread on the rollers and transported along the rollers. An appropriate wire-spinning temperature is selected to promote the wire rods to be in a high-temperature austenite state, and to avoid the formation of network carbides in the wire-spinning stage caused by too low a wire-spinning temperature, so as to form a large temperature gradient later, thereby providing favorable conditions for promoting the troostite phase transformation dominated by fine lamellar spacing. Specifically, the wire-spinning temperature is controlled to be 910℃.

[0062] The online molten salt strong isothermal treatment process adopts a salt bath tank with molten salt inside. The wire rod after spinning is conveyed through the salt bath tank by rollers, so that the wire rod is cooled at a cooling rate of 34°C / s, and quickly passes through the network carbide precipitation interval from the high-temperature austenite state and enters the sorbite phase area, inhibiting the formation of network carbides, promoting the phase transformation of high-temperature austenite to sorbite, forming a structure dominated by sorbite with fine lamellar spacing, and promoting the large-scale dispersion and precipitation of vanadium-containing carbides. As the phase transformation ends, the wire rod enters the high-temperature isothermal interval, promoting the wire rod structure to undergo enhanced isothermal treatment, promoting the transformation of carbides to spheroidized structures, and improving the strength and plasticity matching of the wire rod. Specifically: the molten salt temperature of the online molten salt strong isothermal treatment is 576°C, the treatment time is 465s, the molten salt circulation volume is 520t / h, and the molten salt temperature rise is ≤10°C.

[0063] The roller slow cooling process adopts an open insulation cover, and the conveyor roller conveys the wire rod passing through the salt bath tank into the insulation cover to prevent the wire rod from increasing stress during the cooling process, and promotes further toughening of the wire rod structure, thereby improving the softening effect of the wire rod. Specifically: the wire rod is controlled to be slowly cooled at a cooling rate of 0.3°C / s above 300°C; 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. Its metallographic structure diagram is as follows Figure 3 shown.

[0064] Comparative Example 5:

[0065] A method for manufacturing a hot-rolled wire rod, the manufacturing method of which is different from that of Example 2 in that the processing time of the online molten salt intensive isothermal treatment is 650s, and a hot-rolled wire rod finished product is obtained after going offline.

[0066] Comparative Example 6:

[0067] A method for manufacturing a hot-rolled wire rod, the manufacturing method of which is different from that of Example 2 in that the processing time of the online molten salt intensive isothermal treatment is 300s, and a hot-rolled wire rod finished product is obtained after going offline. Embodiment 4:

[0068] A preferred embodiment of the manufacturing method of the 2060MPa grade hot-rolled wire rod for bridge cables of the present invention, the chemical composition and mass percentage of the hot-rolled wire rod include C: 0.91%, Si: 0.70%, Mn: 0.90%, Cr: 0.45%, V: 0.028%, Nb: 0.025%, P: 0.012%, S: 0.013%, and the rest are Fe and unavoidable impurities; the manufacturing method thereof is manufactured according to the process flow of rolling → spinning → online molten salt strong isothermal treatment → roller slow cooling → coiling, specifically:

[0069] The rolling process is used to heat a steel billet with a specification of 220mm×220mm through a heating furnace to obtain a high-temperature steel billet that can be rolled into plasticity, control the parameters of the heating furnace to promote uniform diffusion of components in the steel billet, reduce segregation and control decarburization, and after the steel billet leaves the heating furnace, roll the steel billet into a wire with a diameter of 15mm through a rolling line, select a suitable rolling temperature and deformation, and use the Nb element precipitation phase to pin the grain boundary to promote dynamic recrystallization and refine the grains during the final rolling process. Specifically: control the heating furnace soaking temperature to 1135°C, and when the furnace is The time interval is 180min, the initial rolling temperature is 1075℃, the final rolling temperature is 940℃, and the final rolling reduction is 25%; the wire-spinning process is used to convert the wire rods coming out of the rolling line into wire rods through a wire-spinning mechanism, and the wire rods are spread on the rollers and transported along the rollers. An appropriate wire-spinning temperature is selected to promote the wire rods to be in a high-temperature austenite state, and to avoid the formation of network carbides in the wire-spinning stage caused by too low a wire-spinning temperature, so as to form a large temperature gradient later, thereby providing favorable conditions for promoting the troostite phase transformation dominated by fine lamellar spacing. Specifically, the wire-spinning temperature is controlled to be 920℃.

[0070] The online molten salt strong isothermal treatment process adopts a salt bath tank with molten salt inside. The wire rod after spinning is conveyed through the salt bath tank by rollers, so that the wire rod is cooled at a cooling rate of 37°C / s, and quickly passes through the network carbide precipitation interval from the high-temperature austenite state and enters the sorbite phase area, inhibiting the formation of network carbides, promoting the phase transformation of high-temperature austenite to sorbite, forming a structure dominated by sorbite with fine lamellar spacing, and promoting the large-scale dispersion and precipitation of vanadium-containing carbides. As the phase transformation ends, the wire rod enters the high-temperature isothermal interval, promoting the wire rod structure to undergo enhanced isothermal treatment, promoting the transformation of carbides to spheroidized structures, and improving the strength and plasticity matching of the wire rod. Specifically: the molten salt temperature of the online molten salt strong isothermal treatment is 545°C, the treatment time is 400s, the molten salt circulation volume is 620t / h, and the molten salt temperature rise is ≤10°C.

[0071] The roller slow cooling process adopts an open insulation cover, and the wire rod passing through the salt bath tank is transported by the conveying roller into the insulation cover to prevent the stress of the wire rod from increasing during the cooling process, promote further toughening of the wire rod structure, and improve the softening effect of the wire rod. Specifically: the wire rod is controlled to be slowly cooled at a cooling rate of 0.2°C / s above 300°C; 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.

[0072] Comparative Example 7:

[0073] A method for manufacturing a hot-rolled wire rod, which differs from Example 3 in that: the method is manufactured according to the process flow of rolling → spinning → online molten salt strong isothermal treatment → air cooling, and the air cooling process adopts the method of opening a heat preservation cover, and conveying the wire rod through a salt bath tank by a conveyor roller, and controlling the wire rod to cool at a temperature above 300°C and a cooling rate of 1.1°C / s, and obtaining a hot-rolled wire rod finished product after it comes off the line.

[0074] The hot rolled wire rods obtained in the above examples 1 to 4 and comparative examples 1 to 7 were subjected to microstructure and performance testing, and the comparative results obtained are shown in Table 1 below:

[0075] Table 1. Comparison of microstructure and performance of hot rolled wire rods with different compositions and manufacturing methods

[0076]

[0077] The interlamellar spacing in Table 1 refers to the interlamellar spacing of tempered troostite or troostite or tempered pearlite. It can be seen from the comparison results of Example 1 and Comparative Example 1 that the requirements for the parent material hot-rolled wire rod are extremely stringent compared to the 2060MPa-level bridge cable. The hot-rolled wire rod structure is controlled by the Stelmor air-cooling line. The extremely high C content and alloy content will cause the wire rod to be extremely difficult to control the deterioration of the structure such as carbon and martensite that affects the performance of the finished wire rod during the production process, and it is difficult to produce stably, which leads to a very high risk of wire breakage in the wire drawing process. The present invention combines the online molten salt strong isothermal technology with the C-Si-Mn-Cr-Nb-V chemical composition design. , controlling the rapid entry from the high-temperature austenite state into the troostite phase region, forming a structure dominated by troostite with fine lamellar spacing, and promoting the isothermal strengthening of the wire rod structure, which can effectively control the deterioration of the structure that affects the performance of the finished wire rod during the production process, improve the strength-plasticity matching of the wire rod, and make it easier to produce stably. It can be seen from the results of Examples 1 to 4 that the product microstructure type includes a mixed structure composed of tempered troostite, ferrite, and micro-spheroidized carbide, with a tensile strength of 1440~1490MPa and a cross-sectional shrinkage rate of 42%~46%, which can be used to manufacture 2060MPa-level ultra-high strength bridge cables and other application fields to meet application needs.

[0078] From the comparison results of Example 1 and Comparative Example 2, it can be seen that selecting a higher spinning temperature can reduce the restriction on the rolling temperature, so as to promote the precipitation phase of the Nb element to pin the grain boundaries and refine the grains, inhibit the growth of austenite grains, and avoid the formation of network cementite in the spinning stage, thereby providing favorable conditions for controlling the refinement of network carbides and troostite phase transformation.

[0079] From the comparison results of Example 2 and Comparative Example 3, it can be seen that the higher the molten salt temperature of the online molten salt strong isothermal treatment, the larger the spacing between the troostite lamellae will be, and more thermal power can be provided for tissue softening, thereby reducing the strength of the wire rod and increasing the plasticity. However, if the molten salt temperature is too high, the cooling rate of the wire rod will decrease, which is not conducive to controlling the network carbide and reducing the spacing between the troostite lamellae. At the same time, too high a temperature poses the risk of carbide precipitation and coarsening, resulting in loss of strength and toughness.

[0080] From the comparison results of Example 2 and Comparative Example 4, it can be seen that the lower the molten salt temperature of the online molten salt strong isothermal treatment, the network carbide can be controlled while promoting the nucleation of troostite and the refinement of lamellae, and more driving force can be provided for the large-scale dispersion and precipitation of V-containing carbides in the crystal, thereby improving the matrix strength. However, if the molten salt temperature is too low, it will be unfavorable for the isothermal transformation of organizational strengthening and carbide spheroidization, and will bring about a large plastic loss.

[0081] From the comparison results of Example 3 and Comparative Example 5, it can be seen that the longer the treatment time of the online molten salt strong isothermal treatment, the more complete the transformation of austenite to troostite, the better the softening effect, the lower the stress of the wire rod, and the higher the plasticity. However, if the treatment time is too long, there is a risk of precipitation phase or carbide aggregation and growth, resulting in loss of strong and plastic properties, and it will also cause an increase in production energy consumption.

[0082] From the comparison results of Example 3 and Comparative Example 6, it can be seen that the shorter the treatment time of the online molten salt strong isothermal treatment, the lower the strengthening isothermal effect and the lower the plasticity of the wire rod. However, if the treatment time is too short, it will affect the troostite phase transformation, the microstructure strengthening isothermal or the large-scale precipitation of precipitation phases such as V and Cr, resulting in loss of strength and plasticity.

[0083] From the comparison results of Example 4 and Comparative Example 7, it can be seen that the use of roller slow cooling can prevent the stress increase of the wire rod during the cooling process, promote further toughening of the wire rod structure, and improve the softening effect of the wire rod.

[0084] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for manufacturing a 2060MPa 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, wherein the chemical composition and mass percentage of the hot-rolled wire rod include: C: 0.87%~0.91%, Si: 0.70%~0.85%, Mn: 0.72%~0.90%, Cr: 0.25%~0.45%, V: 0.02%~0.03%, Nb: 0.015%~0.025%, P≤0.015%, S≤0.015%, and the rest are Fe and unavoidable impurities; the wire rod is spun into a wire rod at a spinning temperature of ≥910°C, and then subjected to online melting The salt strong isothermal treatment causes the wire rod to be cooled at a cooling rate of ≥34°C / s, entering the sorbite phase region from the austenite state, forming a structure dominated by sorbite with fine lamellar spacing and isothermally treated to promote carbide spheroidization, and finally slowly cooled through a roller to form a hot-rolled wire rod with a microstructure dominated by tempered sorbite and the rest being a mixed structure composed of ferrite and micro-spheroidized carbides; the molten salt temperature of the online molten salt strong isothermal treatment is 545~590°C, the treatment time is 400~550s, the molten salt circulation volume is 520~620t / h, and the molten salt temperature rise is ≤10°C.

2. The method for manufacturing the 2060MPa grade hot-rolled wire rod for bridge cables according to claim 1, characterized in that: Before the rolling, the soaking temperature of the heating furnace is controlled to be 1120-1170° C., and the time in the furnace is 120-220 min.

3. The method for manufacturing the 2060MPa 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 1070-1100° C., the final rolling temperature is controlled to be 930-980° C., and the final rolling reduction is controlled to be 25%-31%.

4. The method for manufacturing 2060MPa grade hot rolled wire rod for bridge cables according to claim 1, characterized in that: The roller slow cooling controls the wire rod to be slowly cooled at a cooling rate of 0.2-0.4°C / s above 300°C.

5. A 2060MPa grade hot-rolled wire rod for bridge cables, characterized in that: The hot-rolled wire rod is manufactured by the method for manufacturing 2060MPa grade hot-rolled wire rod for bridge cables according to any one of claims 1 to 4.

6. The 2060MPa grade hot rolled wire rod for bridge cables according to claim 5, characterized in that: The volume percentage of the tempered troostite is ≥90%, and the interlamellar spacing of the tempered troostite is 75-120 mm.

7. The 2060MPa 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 ≤50MPa.

8. The 2060MPa grade hot rolled wire rod for bridge cables according to claim 7, characterized in that: The hot-rolled wire rod has a diameter of 12.0-15.0 mm, a tensile strength of 1440-1490 MPa, and a cross-sectional shrinkage of 42%-46%.

Images