High-performance bonding-controllable prestressed component

Abstract

The utility model discloses a high-performance bonding-controllable prestressed member which comprises a heating assembly and a prestressed tendon applied to a concrete part, and the prestressed tendon comprises a sleeve arranged in the concrete part; the steel strand is arranged in the sleeve and extends in the axial direction of the sleeve, a gap is formed between the steel strand and the inner wall of the sleeve, the tensile strength of the steel strand reaches 2160 Mpa or above, the stress corrosion resistance reaches the minimum value of 2 hours, and the stress corrosion resistance reaches the median value of 5 hours or above; the controllable bonding layer is arranged in the gap between the sleeve and the steel strand, and the heating assembly is used for heating and curing the controllable bonding layer. According to the prestressed member, high corrosion resistance of the ultrahigh-strength prestressed steel strand can be achieved, the external sleeve of the steel strand can be further effectively protected and prevented from corrosion, the service life is remarkably prolonged, the curing time of the controllable bonding material is controllable, the prestressed tendons can be rapidly cured after being tensioned, the curing waiting period is shortened, the project progress can be accelerated, and the construction efficiency is improved. And the structural safety is improved.

Description

Technical Field

[0001] This application belongs to the field of prestressing technology, specifically relating to a high-performance, controllable-bonding prestressed component. Background Technology

[0002] The durability of prestressed tendons has a significant impact on the performance of prestressed structures; therefore, the durability guarantee rate of prestressed tendons should be higher than that of ordinary steel bars. Especially when structures face complex environmental conditions, simply improving the material quality and thickness of the concrete cover often cannot guarantee the design service life. With the increase in the strength grade of steel strands, their stress corrosion sensitivity under high-stress environments increases significantly, which is detrimental to the application of ultra-high strength steel strands.

[0003] Especially in the field of wind power technology, the prestressed components such as anchors or high-strength bolts used in current wind turbine foundations are all unbonded prestressed structures. Generally, Dacromet coating is applied to their outer surface for corrosion protection. In practice, PVC pipes are usually fitted over the anchors and high-strength bolts to ensure a non-bonded relationship between them and the concrete. After tensioning, the top of the PVC pipe is sealed to prevent water ingress. However, the waterproof sealing process for the top of the PVC pipe is usually complex and flawed, allowing rainwater to enter. Since Dacromet loses its corrosion resistance when exposed to water, foundations constructed using this method suffer from severe corrosion of the prestressed components, seriously threatening the safety of the wind turbine. Currently, wind turbine towers mainly use external prestressed structures and prestressed cables. The external prestressing tendons are in direct contact with the external environment, especially in harsh corrosive environments such as coastal areas. Therefore, it is urgent to improve the adaptability and corrosion resistance of this key component—the prestressing tendons—in the operating environment and extend its service life. Utility Model Content

[0004] The purpose of this application is to provide a high-performance, controllable-bonding prestressed member to solve the technical problem that existing prestressed tendons have low corrosion resistance and cannot guarantee the design service life.

[0005] To achieve the above objectives, a first aspect of this application provides a high-performance, controllable-bonding prestressed member, including a heating assembly and prestressing tendons applied in a concrete component, the prestressing tendons comprising:

[0006] A sleeve is arranged within the concrete component;

[0007] A steel strand is arranged inside the sleeve, the steel strand extends along the axial direction of the sleeve, and a gap is formed between the steel strand and the inner wall of the sleeve. The tensile strength of the steel strand reaches 2160 MPa or above, and the minimum stress corrosion test time of the steel strand in solution A reaches 2 hours or above, and the median reaches 5 hours or above.

[0008] A controllable adhesive layer is disposed at the gap between the sleeve and the steel strand;

[0009] The heating component is used to heat and cure the controllable adhesive layer.

[0010] Among them, the stress corrosion test shall be carried out in accordance with the provisions of the current national standard GB / T 21839 "Test Methods for Steel for Prestressed Concrete".

[0011] In one or more embodiments, the controllable adhesive layer is an epoxy resin layer, and the controllable adhesive layer uniformly fills the gap between the steel strand and the sleeve, and the thickness of the controllable adhesive layer in the radial direction of the steel strand is 1.15 to 1.25 mm.

[0012] In one or more embodiments, the steel strand is obtained by twisting 19 wire rods together, the nominal diameter of the steel strand is 21.8–28.6 mm, and the nominal area of ​​the steel strand is 313–532 mm². 2 .

[0013] In one or more embodiments, the steel strand is obtained by twisting seven wire rods together, the nominal diameter of the steel strand is 15.2–21.6 mm, and the nominal area of ​​the steel strand is 140–285 mm². 2 .

[0014] In one or more embodiments, the heating assembly includes a power source electrically connected to the steel strand.

[0015] In one or more embodiments, the steel strand includes tensioning ends located at both ends, the tensioning ends extending out of the sleeve and the concrete component, and the power source is connected to the two tensioning ends of the steel strand.

[0016] In one or more embodiments, the prestressing tendons include at least two spaced prestressing tendons, each prestressing tendon having a tensioning end at one end and an anchoring end at the other end, the anchoring end and the tensioning end extending out of the sleeve, the anchoring end being fixed inside the concrete member, and the tensioning end extending out of the concrete member.

[0017] The heating assembly also includes a conductive clamp located inside the concrete component and connected to the anchoring end of the adjacent steel strand;

[0018] The power source is connected to the tensioning end of the adjacent steel strand.

[0019] In one or more embodiments, the conductive clamp is a U-shaped conductive clamp, and the conductive clamp is clamped and fixed between the anchor ends of adjacent steel strands.

[0020] In one or more embodiments, the heating assembly further includes a variable resistor arranged on the connection circuit between the power supply and the steel strand.

[0021] In one or more embodiments, the outer wall of the sleeve is formed with a plurality of longitudinal ribs distributed in a ring and a plurality of transverse ribs spaced apart along the axial direction of the sleeve. The longitudinal ribs extend along the axial direction of the sleeve, and the transverse ribs extend along the circumferential direction of the sleeve. Each transverse rib connects to the plurality of longitudinal ribs.

[0022] In one or more embodiments, the steel strand is obtained by twisting multiple wire rods together, wherein the wire rods have a sorbitization rate greater than or equal to 95%, the spacing between the sorbite lamellars is 50–70 nm, and the chemical composition of the wire rods, by mass percentage, includes:

[0023] C 0.85–0.91%, Si 0.3–1.0%, Mn 0.2–0.8%, Cr 0.15–0.45%, V 0.02–0.05%, S ≤0.008%, P ≤0.010%, N ≤0.004%, O ≤0.0020%, balance Fe and other unavoidable impurities.

[0024] In one or more embodiments, the steel strand is prepared by the following steps:

[0025] Molten steel is smelted to obtain target molten steel, the chemical composition of which, by mass percentage, comprises: C 0.85–0.91%, Si 0.3–1.0%, Mn 0.2–0.8%, Cr 0.15–0.45%, V 0.02–0.05%, S ≤ 0.008%, P ≤ 0.010%, N ≤ 0.004%, O ≤ 0.0020%, with the balance being Fe and other unavoidable impurities;

[0026] The target molten steel is cast into an intermediate billet by continuous casting of small square billets.

[0027] The intermediate billet is subjected to a high-speed wire rolling process to obtain a coil;

[0028] The coil is immediately immersed in a salt bath for online isothermal treatment. After treatment, the coil is immediately placed in an insulated corridor for online aging and temperature control treatment. After treatment, it is cooled to room temperature to obtain the wire rod.

[0029] The steel strand is prepared by sequentially subjecting multiple wire rods to pickling, phosphating, drawing, twisting and stabilizing processes.

[0030] The online salt bath isothermal treatment is performed at a salt bath temperature of 530–560°C for 100–250 seconds, and the average cooling rate of the temperature control treatment is no higher than 0.2°C / s.

[0031] The advantages of this application, which differ from existing technologies, are:

[0032] The prestressed components of this application achieve high corrosion resistance of ultra-high strength prestressed steel strands. By using external sleeves for the steel strands, the corrosion protection is further effectively enhanced, significantly extending their service life. At the same time, the curing time of the controllable bonding material of the prestressed components is controllable. The controllable bonded prestressing tendons can be cured quickly after tensioning, greatly shortening the curing waiting period, which is conducive to accelerating the project progress and improving structural safety.

[0033] This application significantly improves the strength, plasticity, and homogeneity of wire rod by optimizing the chemical composition ratio, reasonable preparation process parameters, and post-rolling controlled cooling process. This allows the wire rod to achieve ultra-high strength of over 2300MPa with less reduction in surface area during subsequent steel strand preparation. Reducing the reduction in surface area during drawing and significantly improving the plasticity index of the wire rod can reduce surface damage and internal defects of the wire rod during subsequent drawing processing, thereby improving the stress corrosion index of the steel strand.

[0034] The steel strand of this application has a sorbitization rate of 95%, a sorbite lamellar spacing of 50-70 nm, and a tensile strength of over 1425 MPa. The steel strand of this application has a tensile strength of over 2300 MPa, which is beneficial for reducing carbon emissions and material consumption. At the same time, it has excellent stress corrosion resistance. Taking the prepared 1×7 steel strand as an example, the minimum stress corrosion resistance is 2.5 hours and the median is 5 hours, which is significantly higher than the minimum value of 0.7 hours and the median of 1.2 hours recommended by the existing ultra-high strength related standards. Based on the existing standard requirement of a design service life of 50 years, the service life of the prestressed tendon of this application can be estimated to reach about 175 years based on the corrosion resistance time.

[0035] As the strength level of steel strands increases, their stress corrosion sensitivity under high stress environments increases significantly. This application clarifies the applicability of steel strands of different strength levels in corrosive media, avoids sacrificing durability due to increased strength, and enhances the positive role of ultra-high strength materials in energy conservation and carbon reduction. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a structural schematic diagram of an embodiment of the high-performance controllable bonding prestressed member of this application;

[0038] Figure 2 This is a cross-sectional structural schematic diagram of the prestressed tendon of the present application—an embodiment;

[0039] Figure 3 This is a structural schematic diagram of another embodiment of the high-performance controllable bonding prestressed member of this application;

[0040] Figure 4 This is a flowchart illustrating the method for preparing the steel strand of this application;

[0041] Figure 5 These are metallographic images of the wire rod prepared in Example 1 of this application;

[0042] Figure 6 These are metallographic images of the wire rod prepared in Example 2 of this application;

[0043] Figure 7 These are metallographic images of the wire rod prepared in Example 3 of this application.

[0044] As shown in the figure:

[0045] Prestressed tendon 100; sleeve 101; transverse rib 1011; longitudinal rib 1012; steel strand 102; wire rod 1021; tensioning end 1022; anchoring end 1023; controllable bonding layer 103;

[0046] Heating component 200; power supply 201; variable resistor 202; conductive clamp 203. Detailed Implementation

[0047] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of this application.

[0048] To address the technical problem of low corrosion resistance in existing prestressed tendons, which cannot guarantee the design service life, the applicant has developed a new type of prestressed component. This prestressed component enables ultra-high strength prestressed steel strands to have high stress corrosion resistance and provides further effective protection against corrosion from the external sleeves of the steel strands. This significantly extends their service life, helps reduce carbon emissions and material consumption, accelerates project progress, and improves structural safety.

[0049] Specifically, please refer to Figure 1 , Figure 1 This is a structural schematic diagram of one embodiment of the high-performance controllable bonding prestressed component of this application.

[0050] like Figure 1 As shown, the prestressed member includes a heating assembly 200 and prestressing tendons 100 applied in a concrete member 300. The prestressing tendons 100 include sleeves 101 arranged in the concrete member and steel strands 102 arranged inside the sleeves 101.

[0051] The steel strand 102 extends axially along the sleeve 101, and a gap is formed between the steel strand 102 and the inner wall of the sleeve 101.

[0052] The prestressed member also includes a controllable adhesive layer 103 disposed in the gap between the sleeve 101 and the steel strand 102, and the heating assembly 200 is used to heat and cure the controllable adhesive layer 103.

[0053] Understandably, by wrapping the steel strand 102 with the controllable adhesive layer 103, the steel strand 102 can be effectively protected, preventing it from being corroded, thereby increasing its service life.

[0054] To ensure the protective effect, in this embodiment, the controllable adhesive layer 103 can be an epoxy resin layer, and the controllable adhesive layer 103 uniformly fills the gap between the steel strand 102 and the sleeve 101. The thickness of the controllable adhesive layer 103 in the radial direction of the sleeve 101 is 1.15 to 1.25 mm.

[0055] Specifically, in one embodiment, a single-component epoxy resin, obtained by mixing epoxy resin, thermotropic latent curing agent, modifier, and filler, can be injected into the gap between the steel strand 102 and the sleeve 101, and after curing, a controllable adhesive layer 103 is formed.

[0056] In this embodiment, a heating component 200 is also provided to accelerate the curing of the controllable adhesive layer 103 by heating it, thereby significantly improving the fixing speed of the controllable adhesive layer 103. During construction, the controllable adhesive material can be filled into the gap between the steel strand 102 and the sleeve 101. Then, the steel strand 102 is tensioned. After tensioning, the controllable adhesive material is quickly cured by heating to form a controllable adhesive layer 103 that completely wraps the steel strand 102.

[0057] Specifically, in this embodiment, both ends of the steel strand 102 extend out of the concrete component 300, thereby forming tension ends 1022 at both ends of the steel strand 102. In the subsequent tensioning process, the tensioning operation of the steel strand 102 can be performed through the tension ends 1022 at both ends.

[0058] The heating assembly 200 may include a power supply 201 electrically connected to the two tension ends 1022 of the steel strand 102. The power supply 201 can supply low voltage and high current into the steel strand 102 to heat the steel strand 102 and transfer the heat to the controllable bonding material to accelerate its curing.

[0059] In order to control the heating current, the heating component 200 in this embodiment also includes a variable resistor 202 arranged on the connection circuit between the power supply 201 and the steel strand 102. By adjusting the size of the variable resistor 202, the heating current can be controlled, thereby accurately controlling the heating of the controllable adhesive material.

[0060] In this embodiment, the sleeve 101 can be a plastic sleeve 101. To improve its strength, please refer to [reference needed]. Figure 1 and Figure 2 , Figure 2 This is a cross-sectional structural schematic diagram of one embodiment of the prestressed tendon 100 of this application. Figure 1 and Figure 2 As shown, the outer wall of the sleeve 101 is formed with two longitudinal ribs 1012 distributed at 180° and a plurality of transverse ribs 1011 arranged at intervals along the axial direction of the sleeve 101. The longitudinal ribs 1012 extend along the axial direction of the sleeve 101, and the transverse ribs 1011 extend circumferentially along the sleeve 101. Each transverse rib 1011 connects to a plurality of longitudinal ribs 1012, thereby significantly improving the strength of the sleeve 101.

[0061] It should be understood that in other embodiments, the number of longitudinal ribs 1012 and transverse ribs 1011 can be adjusted based on actual needs, or only longitudinal ribs 1012 or only transverse ribs 1011 can be set, all of which can achieve the effect of this embodiment to a certain extent.

[0062] For further details, please refer to Figure 2In this embodiment, the steel strand 102 has a specification of 1*19, meaning it is obtained by twisting 19 wire rods 1021 together. The nominal diameter of the steel strand 102 is 21.8–28.6 mm, and the nominal area of ​​the steel strand 102 is 313–532 mm². 2 .

[0063] In other embodiments, the steel strand 102 can also be obtained by twisting other numbers of wire rods 1021. For example, the steel strand 102 can also be 1*7, that is, obtained by twisting 7 wire rods 1021. The nominal diameter of the steel strand can be 15.2 to 21.6 mm, and the nominal area of ​​the steel strand can be 140 to 285 mm². 2 This also satisfies the effect of this implementation method.

[0064] In this embodiment, the stress corrosion resistance of the steel strand 102 reaches a minimum of 2 hours or more and a median of 5 hours or more.

[0065] Specifically, the stress corrosion resistance performance reaching a minimum of 2 hours or more and a median of 5 hours or more means that when the steel strand of this embodiment is subjected to stress corrosion test in solution A according to standard GB / T 15970.6-2007, the minimum test time reaches 2 hours or more and the median reaches 5 hours or more.

[0066] In the above embodiment, the prestressing tendon 100 is tensioned at both ends, with both ends of the steel strand 102 extending out of the concrete member 300. In another embodiment, the prestressing tendon 100 may also be tensioned at one end, with only one end of the steel strand 102 extending out of the concrete member 300. Please refer to [link to previous embodiment]. Figure 3 , Figure 3 This is a structural schematic diagram of another embodiment of the high-performance controllable bonding prestressed component of this application.

[0067] like Figure 3 As shown, the prestressed member includes two prestressing tendons 100. The steel strand 102 of each prestressing tendon 100 includes a tensioning end 1022 at one end and an anchoring end 1023 at the other end. The anchoring end 1023 and the tensioning end 1022 extend out of the sleeve 101. The anchoring end 1023 is fixed inside the concrete member 300, and the tensioning end 1022 extends out of the concrete member 300.

[0068] In this embodiment, the heating assembly 200 also includes a conductive clamp 203, which is located inside the concrete component 300 and connected to the anchoring end 1023 of the adjacent steel strand 102.

[0069] Specifically, in this embodiment, the conductive clamp 203 is a U-shaped conductive clamp 203, and the conductive clamp 203 is clamped and fixed between the anchor ends 1023 of adjacent steel strands 102.

[0070] In this embodiment, the power supply 201 is connected to the tensioning end 1022 of the adjacent steel strand 102, thereby forming a loop and simultaneously heating and curing the controllable bonding material of the two prestressed tendons 100.

[0071] The prestressed components based on the above embodiments can effectively protect the steel strands 102 and significantly extend their service life. At the same time, the curing time of the controllable bonding material of the prestressed components is controllable. After tensioning, the controllable bonded prestressing tendons 100 can be cured quickly, which greatly shortens the curing waiting period, helps to accelerate the project progress and improve structural safety.

[0072] To further improve the stress corrosion resistance and strength of prestressed tendons, the material and preparation method of the steel strand in this application have been improved. Specifically, the chemical composition of the steel strand wire rod in this application, by mass percentage, includes:

[0073] C 0.85–0.91%, Si 0.3–1.0%, Mn 0.2–0.8%, Cr 0.15–0.45%, V 0.02–0.05%, S ≤0.008%, P ≤0.010%, N ≤0.004%, O ≤0.0020%, balance Fe and other unavoidable impurities.

[0074] This application significantly improves the homogeneity of steel and enhances its stress corrosion index by optimizing the mass fraction of each chemical component in the wire rod.

[0075] Specifically, this application limits the C content to 0.85–0.91% to ensure high tensile strength of the wire rod; limits the Si content to 0.3–1.0% to improve the corrosion resistance and relaxation resistance of the steel; limits the Mn content to 0.2–0.8% to improve the strength and hardenability of the steel and ensure good work hardening rate of the wire rod; limits the Cr content to 0.15–0.45% to obtain retained austenite and form a dense oxide film on the steel surface, while avoiding excessive Cr content which increases the difficulty of segregation control; and limits the V content to 0.02–0.05% to allow the carbon oxides formed by V to act as effective hydrogen traps in the steel, improving the stress corrosion index of the steel.

[0076] In addition, in order to avoid affecting the strength and plasticity of the steel, this application limits the S content to less than or equal to 0.008%, the P content to less than or equal to 0.010%, the N content to less than or equal to 0.004%, and the O content to less than or equal to 0.0020%.

[0077] Based on the above content ratio, the stress corrosion resistance of the wire rod can be significantly improved while ensuring its high strength. In one embodiment, the diameter of the wire rod can reach 8-14 mm, the tensile strength can reach 1470-1570 MPa, and the reduction of area can be 35-48%.

[0078] This application also provides a method for preparing steel strand; please refer to [link to relevant documentation]. Figure 4 , Figure 4 This is a schematic flowchart of the method for preparing the steel strand of this application.

[0079] like Figure 4 As shown, the preparation method includes:

[0080] S100, smelt steel to obtain the target molten steel.

[0081] The chemical composition of the target molten steel is consistent with that of the wire rod, which will not be elaborated here, so that wire rod with the target chemical composition can be prepared based on the target molten steel.

[0082] In one implementation, the steps of smelting molten steel may specifically involve sequentially performing converter smelting and LF furnace refining.

[0083] Specifically, the converter smelting process involves sending molten iron into a converter to mix with scrap steel to form molten steel, and then performing desiliconization, dephosphorization, oxygen blowing and decarburization. When tapping the steel, alloys are added to the ladle for deoxidation and alloying.

[0084] LF furnace refining specifically involves sending molten steel from converter smelting into an LF refining furnace for chemical composition adjustment and temperature control. Inclusions in the molten steel are controlled by soft stirring until the temperature of the molten steel reaches the requirements for continuous casting and the chemical composition of the molten steel meets the standards before tapping, thus obtaining the target molten steel.

[0085] S200: Small billet continuous casting is used to cast the target molten steel into an intermediate billet.

[0086] Once the target molten steel with the required temperature and chemical composition is obtained, it can be cast into shape using a continuous casting process.

[0087] In one embodiment, the size of the continuously cast billet can be 180mm × 240mm; in other embodiments, the size of the billet can also be adjusted according to actual needs, and all of these can achieve the effect of this embodiment.

[0088] To ensure the tensile strength and stress corrosion resistance of the prepared wire rod, this application optimizes the parameters of the continuous casting process. Specifically, in one embodiment, the superheat of the target molten steel can be 20-25°C, the stirring current of the crystallizer can be 270±25A, the stirring frequency of the crystallizer can be 3±0.5Hz, the casting speed during continuous casting can be 1.2±0.05m / min, the specific water content during continuous casting can be 0.22±0.01L / kg, the end stirring current can be 450±25A, the end stirring frequency can be 8±0.5Hz, and the total reduction under light pressure can be 15.0±0.2mm.

[0089] S300: The intermediate billet is subjected to a high-speed wire rolling process to obtain a coil.

[0090] The high-speed wire rolling process specifically involves heating the intermediate billet and then sequentially performing rough rolling, finish rolling, and wire drawing to obtain a coil.

[0091] In one embodiment, the heating temperature can be 1080–1150°C, the roughing rolling temperature can be 950–1000°C, and the finishing rolling inlet temperature can be 840–900°C.

[0092] To improve the effectiveness of the subsequent controlled cooling process after rolling, the spinning temperature can be 840–900℃.

[0093] S400: Immediately immerse the coil in a salt bath for online isothermal treatment. After treatment, immediately place the coil into an insulated corridor for online aging and temperature control treatment. After treatment, cool to room temperature to obtain the wire rod.

[0094] After the high-speed wire rolling process, the coil still maintains the wire-spinning temperature of the rolling process. Without uncoiling, the coil is immediately immersed in the salt bath tank to achieve online isothermal treatment in the salt bath, and to precisely control the material structure and properties.

[0095] Compared to traditional offline salt bath heat treatment, the solution in this application does not require unwinding the coil, heat treatment, and then rewinding, thus avoiding surface damage to the steel and helping to improve the stress corrosion index of the steel strand.

[0096] In one embodiment, the salt bath temperature for online salt bath isothermal treatment can be 530–560°C, and the salt bath time can be 100–250 seconds.

[0097] After online salt bath isothermal treatment, the coil can be immediately placed in an insulated corridor for online aging, precisely controlling the coil temperature and thus refining the microstructure of the steel.

[0098] In one implementation, the average cooling rate of the temperature-controlled process is no higher than 0.2°C / s.

[0099] The controlled cooling process after rolling, based on online salt bath isothermal treatment and online aging in the insulation corridor, can refine the microstructure of the wire rod and significantly increase the sorbitization rate to improve the strength and plasticity of the wire rod.

[0100] S500: Steel strands are prepared by sequentially processing multiple wire rods through pickling, phosphating, drawing, twisting and stabilization processes.

[0101] In one embodiment, pickling specifically involves pickling the coil in a 15-20 wt% hydrochloric acid solution for 7-10 minutes at a pickling temperature of 35-42°C. This ensures the thorough removal of hot-rolled iron oxide scale while preventing the coil from absorbing excessive H.

[0102] In one embodiment, phosphating is carried out after the pickled coils have been left to stand for 20–28 hours.

[0103] In one embodiment, the drawing process specifically involves drawing the coil in 9 to 11 passes, with a reduction rate of 23 to 25% per pass, a drawing speed not exceeding 2 m / s, and a temperature rise of not exceeding 100°C per pass.

[0104] Based on the controlled cooling process after rolling of S400, the wire rod has strong plasticity, so the target strength can be achieved with a lower drawing reduction rate, which effectively reduces the surface damage and internal defects of the wire rod, thereby helping to improve the stress corrosion resistance.

[0105] In one embodiment, the tension of the twisted strand can be greater than or equal to 80 kN, the speed can be less than or equal to 36 m / min, and the stabilization temperature of the stabilization process can be 400–430 °C.

[0106] Based on the above-described embodiments of wire rod and its preparation method, by optimizing the chemical composition ratio of the wire rod and the reasonable preparation process parameters and post-rolling controlled cooling process, the strength and plasticity of the wire rod and the homogeneity of the steel are significantly improved. This allows the wire rod to achieve ultra-high strength of over 2300MPa with less reduction in surface area during subsequent steel strand preparation. Reducing the reduction in surface area during drawing and significantly improving the plasticity index of the wire rod can reduce surface damage and internal defects of the wire rod during subsequent drawing processing, thereby improving the stress corrosion index of the steel strand.

[0107] The beneficial effects of the material and preparation method of the steel strand in this application are further explained in detail below with reference to specific embodiments.

[0108] Example 1:

[0109] A 2300-2360MPa grade 1*7 steel strand is prepared using the following process:

[0110] (1) Steel smelting process

[0111] The molten steel is smelted through a series of steps including converter smelting and LF furnace refining to obtain the target molten steel. The chemical composition of the target molten steel is shown in Table 1 below as a percentage by mass.

[0112] In the converter smelting process, molten iron is fed into the converter and mixed with scrap steel to form molten steel. Then, desiliconization, dephosphorization, oxygen blowing and decarburization are carried out. When tapping the steel, alloys are added to the ladle for deoxidation and alloying.

[0113] In the refining process, the molten steel after converter smelting is sent to the LF refining furnace for chemical composition adjustment and temperature control. The inclusions in the molten steel are controlled by soft stirring. The steel is tapped after the temperature and chemical composition meet the standards. The superheat of the target molten steel is 20°C.

[0114] (2) Continuous casting process

[0115] Small billet continuous casting is used to cast the target molten steel into small billets with a cross-sectional dimension of 180mm×240mm.

[0116] The target molten steel superheat is controlled at 20℃, the crystallizer stirring current is 245A, the crystallizer stirring frequency is 2.5Hz, the casting speed during continuous casting is 1.15m / min, the continuous casting specific water volume is 0.21L / kg, the end stirring current is 425A, the end stirring frequency is 7.5Hz, and the total reduction under light pressure is 14.8mm.

[0117] (3) High-speed wire rolling process

[0118] The intermediate billet obtained from the continuous casting process is rolled into wire rod with a diameter of 14 mm by high-speed wire rolling. The heating temperature is 1150℃, the roughing rolling temperature is 1000℃, the finishing rolling inlet temperature is 850℃, and the wire drawing temperature is 850℃.

[0119] (4) Post-rolling controlled cooling process

[0120] After spinning, the coils are directly immersed in a salt bath at a temperature of 530℃ for 250 seconds. After isothermal treatment in the salt bath, the coils are immediately placed in an insulated corridor for slow cooling, with an average cooling rate of 0.15℃ / s.

[0121] (5) Steel strand processing procedures

[0122] The coil is pickled, phosphated and drawn to obtain wire rod, which is then twisted and stabilized to obtain 2300-2360MPa grade steel strand;

[0123] The pickling process uses a 19wt% hydrochloric acid aqueous solution for 8 minutes at 35℃. After pickling, the coil is left to stand for 24 hours before entering the phosphating process. The drawing process involves 11 passes with a 23% reduction in surface area per pass, a drawing speed of 2m / s, and a temperature rise of 100℃ per pass. The twisting tension is 80kN, the speed is 36m / min, and the stabilization temperature is 400℃.

[0124] Examples 2 to 4:

[0125] A 2300-2360MPa grade 1*7 steel strand is prepared in a manner that is basically the same as that in Example 1, except that: 1. The chemical composition of the wire rods in Examples 2 to 4 is different from that in Example 1; 2. The parameters of each process in Examples 2 to 3 are different from those in Example 1.

[0126] The chemical composition of the wire rods in Examples 1 to 4 can be found in Table 1 below, and the process parameters of Examples 1 to 3 can be found in Table 2 below.

[0127] Table 1

[0128]

[0129] Table 2

[0130]

[0131]

[0132] Example of effect 1:

[0133] Metallographic analysis was performed on the wire rods prepared in Examples 1 to 3. The analysis methods included:

[0134] A 10cm length of wire rod was taken from the head of the wire rod to prepare a metallographic sample. After electrolytic polishing, the sample was observed under a scanning electron microscope. Figures 5 to 7 , Figure 5 These are metallographic images of the wire rod prepared in Example 1 of this application. Figure 6 These are metallographic images of the wire rod prepared in Example 2 of this application. Figure 7 These are metallographic images of the wire rod prepared in Example 3 of this application.

[0135] The above tests revealed that the wire rods of Examples 1-3 all had a sorbitic structure. Their metallographic data are shown in Table 3 below. The sorbitization rate of Examples 1 to 3 all reached 95%, and the sorbite lamellar spacing was 50-70 nm, indicating that the wire rods have excellent strength and toughness.

[0136] Table 3

[0137] Example Diameter / mm Soxhletization rate Grain boundary cementite Martensite 1 14 95 0.5 0.5 2 13 95 0 0 3 8 95 0 0

[0138] Example 2:

[0139] The mechanical properties of the wire rods prepared in Examples 1 to 3 were tested using a tensile testing machine. The test methods were based on the test methods and definitions in GB / T228 standard, and the data are shown in Table 4 below.

[0140] Table 4

[0141]

[0142] As can be seen from the data above, the wire rods prepared in Examples 1 to 3 have a tensile strength of over 1425 MPa and a cross-sectional shrinkage rate of over 35%, demonstrating excellent mechanical properties.

[0143] Example of effect 3:

[0144] The steel strands prepared in Examples 1 to 3 were subjected to strength tests, and the test methods were in accordance with the standard GB / T 5224-2020. The data are shown in Table 5 below.

[0145] Table 5

[0146]

[0147] As shown in the table above, the tensile strength of the steel strands in Examples 1 to 3 all reach over 2300 MPa, exhibiting excellent performance and meeting the requirements of the new national standard.

[0148] Example of effect 4:

[0149] The steel strands prepared in Examples 1 to 3 were subjected to stress corrosion resistance tests. The test methods were in accordance with standard GB / T15970.6-2007, and the data in Table 6 below were obtained.

[0150] Table 6

[0151]

[0152] As can be seen from the data above, the steel strands prepared in Examples 1 to 3 all have excellent stress corrosion resistance, with a minimum stress corrosion resistance of 2.5h and a median of 5h, which is far superior to the existing 2300MPa steel strands. Based on the existing standard requirement of a 50-year design service life, the service life of the prestressed tendons used in this application can be estimated to reach approximately 175 years based on the corrosion resistance time.

[0153] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this application. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0154] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high-performance, controllable-bonding prestressed member, characterized in that, Includes a heating assembly and prestressing tendons applied in concrete components, the prestressing tendons comprising: A sleeve is arranged within the concrete component; A steel strand is arranged inside the sleeve, the steel strand extends along the axial direction of the sleeve, and a gap is formed between the steel strand and the inner wall of the sleeve. The tensile strength of the steel strand reaches 2160 MPa or above, and the minimum stress corrosion test time of the steel strand in solution A reaches 2 hours or above, and the median reaches 5 hours or above. A controllable adhesive layer is disposed at the gap between the sleeve and the steel strand; The heating component is used to heat and cure the controllable adhesive layer.

2. The prestressed member according to claim 1, characterized in that, The controllable adhesive layer is an epoxy resin layer, and the controllable adhesive layer uniformly fills the gap between the steel strand and the sleeve. The thickness of the controllable adhesive layer in the radial direction of the steel strand is 1.15 to 1.25 mm. The steel strand is obtained by twisting 19 wire rods together. The nominal diameter of the steel strand is 21.8–28.6 mm, and the nominal area of ​​the steel strand is 313–532 mm². 2 ;or, The steel strand is obtained by twisting 7 wire rods together. The nominal diameter of the steel strand is 15.2–21.6 mm, and the nominal area of ​​the steel strand is 140–285 mm². 2 .

3. The prestressed member according to claim 1, characterized in that, The heating assembly includes a power source electrically connected to the steel strand.

4. The prestressed member according to claim 3, characterized in that, The steel strand includes tensioning ends located at both ends, the tensioning ends extending out of the sleeve and the concrete component, and the power source is connected to the two tensioning ends of the steel strand.

5. The prestressed member according to claim 3, characterized in that, The prestressing tendon includes at least two spaced prestressing tendons, and each prestressing tendon has a tensioning end at one end and an anchoring end at the other end. The anchoring end and the tensioning end extend out of the sleeve. The anchoring end is fixed inside the concrete member, and the tensioning end extends out of the concrete member. The heating assembly also includes a conductive clamp located inside the concrete component and connected to the anchoring end of the adjacent steel strand; The power source is connected to the tensioning end of the adjacent steel strand.

6. The prestressed member according to claim 5, characterized in that, The conductive clamp is a U-shaped conductive clamp, and the conductive clamp is clamped and fixed between the anchor ends of the adjacent steel strands.

7. The prestressed member according to claim 3, characterized in that, The heating assembly also includes a variable resistor arranged in the connection circuit between the power supply and the steel strand.

8. The prestressed member according to claim 1, characterized in that, The outer wall of the sleeve is formed with a plurality of longitudinal ribs distributed in a ring and a plurality of transverse ribs arranged at intervals along the axial direction of the sleeve. The longitudinal ribs extend along the axial direction of the sleeve, and the transverse ribs extend along the circumference of the sleeve. Each transverse rib connects to the plurality of longitudinal ribs.

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