Hot-rolled wire rod for prestressed steel strand and method for manufacturing the same

Abstract

The application discloses a hot-rolled wire rod for prestressed steel strand and a preparation method thereof. The method comprises the following steps: sequentially performing converter smelting, LF refining, and continuous casting to obtain a required casting blank, and then sequentially performing casting blank heating, high-speed wire rolling, Stelmor air cooling line controlled cooling, coiling and packaging to obtain the hot-rolled wire rod for prestressed steel strand. The casting blank is cooled through a water tank before and after final rolling, and the water tank opening degree before final rolling is greater than the water tank opening degree after final rolling. In the controlled cooling process, the roller speed is increased to a constant value in sections. The application mainly comprises high-speed wire rolling and controlled rolling and cooling processes. Through the combination of casting blank heating temperature, heating time, wire spewing temperature control after rolling and sectional controlled cooling technology, the hot-rolled wire rod for prestressed steel strand with good performances is finally obtained. The prestressed steel strand made of the wire rod has a tensile strength greater than or equal to 1960 MPa, and the maximum total elongation rate (L0 greater than or equal to 500 mm) Agt is greater than or equal to 4.5%. The method has the advantages of simple process, low production cost and easy industrialization promotion.

Description

Technical Field

[0001] This invention relates to the field of wire rod production technology, and in particular to a hot-rolled wire rod for prestressed steel strand and its preparation method. Background Technology

[0002] Steel strand is a steel product made by spirally twisting multiple high-strength steel wires. The most commonly used types are galvanized steel strand and prestressed steel strand. Prestressed steel strand is widely used in infrastructure construction. Generally, a tensile strength of 1470–1860 MPa is considered high-strength, and a tensile strength above 1860 MPa is considered ultra-high-strength. Currently, the main strength grade used is 1860 MPa, with a corresponding wire rod tensile strength typically between 1140 and 1200 MPa. With rapid industrial development, lightweighting and high strength have extended to the steel strand industry.

[0003] Therefore, the development of ultra-high strength prestressed steel strand is urgently needed. Ultra-high strength steel strand requires higher strength raw wire rod, and alloying is one method to improve the overall performance of steel. Appropriate alloying elements can be added to steel to simultaneously improve its strength and toughness. For wire rod composition design, there are generally two options: one is a high-carbon, high-silicon composition system with trace amounts of chromium; the other is a high-carbon system with various microalloying elements such as niobium, titanium, and vanadium. Adding multiple microalloying elements such as niobium, titanium, and vanadium results in relatively high alloying costs. Furthermore, due to their low solubility in austenite, higher homogenization temperatures are required during heating to dissolve them into austenite so they can play a role in subsequent rolling and cooling processes. Therefore, adopting a high-carbon, high-silicon composition system is more environmentally friendly and economical.

[0004] The most effective way to improve the strength of raw wire rod is to increase the carbon content. However, excessively high carbon content reduces plasticity, making it difficult to meet the requirements for subsequent steel strand production. Furthermore, it easily leads to segregation, resulting in harmful structures such as grain boundary cementite and martensite during post-rolling phase transformation, which negatively impacts subsequent deep processing and causes drawing fracture. Si, on the other hand, is a ferrite-strengthening element with high solid solution strengthening ability, significantly improving the cold work hardening index of steel while reducing strength loss during heat treatment. Therefore, by combining reasonable composition design with advanced production processes, it is possible to produce hot-rolled wire rods that meet the requirements for ultra-high strength prestressed steel strands.

[0005] For example, Chinese patent application number CN202011236089.3 discloses prestressed steel strand, wire rod for prestressed steel strand and its production method. Specifically, it discloses that the wire rod for prestressed steel strand is prepared by sequentially performing the following steps: pre-desulfurization of molten iron, smelting of molten steel, refining of molten steel, continuous casting, high-speed wire rolling, temperature-controlled cooling and coiling. The finished product has a high carbon content, segregation is difficult to control, and network carbides, martensite and other harmful structures that are not conducive to drawing are easily generated in the later stage.

[0006] For example, Chinese patent application number CN202010503561.9 discloses a hot-rolled wire rod for ultra-high strength steel strand and its preparation method. Specifically, it discloses the process of molten iron pretreatment—converter—refining—VD vacuum treatment—continuous casting—billing—rolling. In this process, the molten iron contains Si: 0.3~0.7%, S≤0.015%, P≤0.120%, Ti≤0.10%, and T≥1250℃. The wire rod prepared by this method belongs to the 1860MPa grade of steel strand wire rod, which cannot meet the needs of subsequent development.

[0007] In view of this, improvements should be made to the existing technology. Summary of the Invention

[0008] The main objective of this invention is to provide a hot-rolled wire rod for prestressed steel strand and its preparation method. The method mainly includes high-speed wire rolling and controlled rolling and cooling processes. By combining the control of billet heating temperature, heating time, post-rolling wire drawing temperature, and segmented controlled cooling technology, a hot-rolled wire rod for prestressed steel strand with excellent performance is finally obtained. The prestressed steel strand made from this wire rod has a tensile strength ≥1960MPa and a maximum total elongation (L0≥500mm) Att≥4.5%. This method has the advantages of simple process, low production cost, and easy industrialization.

[0009] According to one aspect of the present invention, a method for preparing hot-rolled wire rod for prestressed steel strand is provided, comprising: sequentially performing converter smelting, LF refining, and continuous casting to obtain the required billet; then sequentially performing billet heating, high-speed wire rolling, Steyrmo air-cooling line controlled cooling, coiling, and packaging to obtain hot-rolled wire rod for prestressed steel strand; wherein, cooling is performed by water tanks before and after final rolling, the opening degree of the water tank before final rolling is greater than the opening degree of the water tank after final rolling, and in the controlled cooling process, the roller speed is gradually increased to a fixed value.

[0010] According to one embodiment of the present invention, the chemical composition of the hot-rolled wire rod for prestressed steel strand, by weight percentage, is as follows: C: 0.83%–0.87%, Si: 0.50%–0.60%, Mn: 0.60%–0.80%, P≤0.015%, S≤0.010%, Cr: 0.25%–0.35%, Cu≤0.20%, Ni≤0.10%; the remainder being Fe and unavoidable impurities.

[0011] According to one embodiment of the present invention, in the high-speed wire rolling process, the billet homogenization temperature is 1080~1150℃, and the heating time is t=(0.7~1.2)H, where H is the billet thickness.

[0012] According to one embodiment of the present invention, the opening degree of the water tank before final rolling is ≥25%, and the water inflow into the water tank is ≥50m³. 3 / h, outlet water pressure ≥3.5 bar, final rolling temperature 860~880℃.

[0013] According to one embodiment of the present invention, the opening degree of the water tank after final rolling is ≤5%, and the spinning temperature is controlled at 880~900℃, with the temperature difference between the surface and core of the wire rod ≤10℃.

[0014] According to one embodiment of the present invention, the coiled wire after spinning is cooled in a controlled manner on a Stellmore air-cooling line. The initial speed of the roller conveyor is 0.50~0.60m / s, the speed of the roller conveyor in sections 2 to 8 increases by 0.03~0.05m / s each section, and the speed of the roller conveyor in sections 9 to 13 is 0.74~1.00m / s.

[0015] According to one embodiment of the present invention, in the controlled cooling of the Stellmore air-cooled line, the opening degree of the front fan is ≥60%, the heat insulation cover is opened, the opening angle of the Jialing device is 2°~4°, the rapid cooling is 580~620°, and the temperature difference between the surface and the core of the wire rod is ≤15°.

[0016] According to one embodiment of the present invention, the controlled cooling of the Stellmore air-cooled line further includes: turning off the fan and the insulation cover, and slowly cooling at a cooling rate of 1 to 3°C / s, with a winding temperature of 450 to 500°C.

[0017] According to another aspect of the present invention, a hot-rolled wire rod for prestressed steel strand is provided, which is prepared by any of the methods described above.

[0018] According to one embodiment of the present invention, the hot-rolled wire rod for prestressed steel strand has a sorbite content ≥95%, no core martensite, grain boundary cementite grade ≤1.0, tensile strength ≥1250MPa, and reduction of area ≥30%.

[0019] In a method for preparing hot-rolled wire rod for prestressed steel strand according to an embodiment of the present invention, the main processes include high-speed wire rolling and controlled rolling and cooling. By combining the control of billet heating temperature, heating time, post-rolling wire drawing temperature and segmented controlled cooling technology, a hot-rolled wire rod for prestressed steel strand with good performance is finally obtained. The prestressed steel strand made from this wire rod has a tensile strength ≥1960MPa and a maximum total elongation (L0≥500mm) Att≥4.5%. This method has the advantages of simple process, low production cost and easy industrialization. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some implementation examples of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A process flow diagram of a method for preparing hot-rolled wire rod for prestressed steel strand according to an exemplary embodiment of the present invention is shown. Detailed Implementation

[0022] The following detailed description of the embodiments is intended to exemplify the principles of the present invention, but should not be construed as limiting the scope of the invention. The present invention can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0023] These embodiments are provided to make this disclosure thorough and complete, and to fully express the scope of the invention to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​set forth in these embodiments should be interpreted as merely exemplary and not as limiting.

[0024] It should be noted that, in the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0025] It should also be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention depending on the specific circumstances. When a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device.

[0026] All terms used in this invention have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0027] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0028] like Figure 1 As shown, the present invention provides a method for preparing hot-rolled wire rod for prestressed steel strand, which includes the following steps:

[0029] S1, the required billet is obtained by sequentially smelting in a converter, refining in an LF furnace, and continuously casting.

[0030] S2, the process involves sequentially heating the billet, high-speed wire rolling, controlled cooling in the Steyrmo air-cooling line, coiling and packaging to produce hot-rolled wire rods for prestressed steel strands.

[0031] In this process, cooling is carried out through water tanks before and after final rolling. The opening degree of the water tank before final rolling is greater than that after final rolling. During the cooling process, the speed of the roller table is gradually increased to a fixed value.

[0032] The method for preparing hot-rolled wire rod for prestressed steel strand according to an embodiment of the present invention mainly includes high-speed wire rolling and controlled rolling and cooling processes. By combining the control of billet heating temperature, heating time, post-rolling wire drawing temperature and segmented controlled cooling technology, hot-rolled wire rod for prestressed steel strand with good performance is finally obtained. The prestressed steel strand made from this wire rod has a tensile strength ≥1960MPa and a maximum total elongation (L0≥500mm) Att≥4.5%. This method has the advantages of simple process, low production cost and easy industrialization.

[0033] In some specific embodiments, the chemical composition of the hot-rolled wire rod for prestressed steel strand, by weight percentage, is as follows: C: 0.83%–0.87%, Si: 0.50%–0.60%, Mn: 0.60%–0.80%, P≤0.015%, S≤0.010%, Cr: 0.25%–0.35%, Cu≤0.20%, Ni≤0.10%; the remainder being Fe and unavoidable impurities.

[0034] Based on the above embodiments, in the high-speed wire rolling process, the billet homogenization temperature is 1080~1150℃, and the heating time is t=(0.7~1.2)H, where H is the billet thickness.

[0035] In some specific embodiments, the opening degree of the water tank before final rolling is ≥25%, and the water inflow into the water tank is ≥50m³. 3The water flow rate is ≥3.5 bar, and the final rolling temperature is 860–880℃. By increasing the opening degree of the water tank before final rolling, the temperature of the rolled piece before entering the finishing mill can be effectively reduced, thereby allowing for more precise control of the final rolling temperature. This is particularly important for steels that require a specific final rolling temperature to obtain ideal microstructure and mechanical properties. A larger opening degree means stronger cooling capacity, which helps reduce temperature fluctuations caused by various factors during rolling (such as speed fluctuations, transport time, etc.) and improves the stability of the final rolling temperature.

[0036] Based on the above embodiments, the opening degree of the water tank after final rolling is ≤5%, and the wire drawing temperature is controlled at 880~900℃, with the temperature difference between the surface and core of the wire rod ≤10℃.

[0037] In some specific embodiments, the coiled wire after spinning is cooled in a controlled manner on a Stellmore air-cooling line. The initial speed of the roller conveyor is 0.50~0.60m / s, the speed of the roller conveyor in sections 2 to 8 increases by 0.03~0.05m / s each section, and the speed of the roller conveyor in sections 9 to 13 is 0.74~1.00m / s.

[0038] Gradually increasing the roller speed ensures that adjacent coils gradually increase in spacing during air cooling, reducing heat transfer between coils and thus improving cooling uniformity. Optimizing the roller speed can also refine the wire grains, thereby increasing its tensile strength.

[0039] Specifically, the coiled wire after spinning is cooled in a controlled manner on the Stellmore air-cooling line. The initial speed of the roller conveyor is 0.56 m / s, and the speed of the roller conveyor in sections 2 to 8 increases by 0.04 m / s each time, with the speed in sections 9 to 13 being 0.88 m / s.

[0040] Based on the above embodiments, in the Stellmore air-cooled line controlled cooling, the front fan opening degree is ≥60%, the insulation cover is open, the opening angle of the Jialing device is 2°~4°, rapid cooling is achieved to 580~620°C, and the temperature difference between the surface and core of the wire rod is ≤15°C. Specifically, the opening angle of the Jialing device is 3°.

[0041] In some specific embodiments, the fan and insulation cover are turned off, and slow cooling is carried out at a cooling rate of 1 to 3°C / s, with the winding temperature being 450 to 500°C.

[0042] The present invention also proposes a hot-rolled wire rod for prestressed steel strand, which is prepared by the method mentioned in the above technical solution.

[0043] In some specific embodiments, the hot-rolled wire rods used for prestressed steel strands have a sorbite content of ≥95%, no core martensite, grain boundary cementite grade ≤1.0, tensile strength ≥1250MPa, and reduction of area ≥30%.

[0044] This hot-rolled wire rod can be used to make 1×19S-21.8mm prestressed steel strands with a tensile strength ≥1960MPa and a maximum total elongation (L0≥500mm)Agt≥4.5%.

[0045] One specific application of this invention is as follows:

[0046] Step 1: The required billet is obtained by converter smelting, LF refining and continuous casting. The billet composition is C 0.83%~0.87%, Si 0.50%~0.60%, Mn 0.60%~0.80%, P≤0.015%, S≤0.010%, Cr 0.25%~0.30%, Cu≤0.20%, Ni≤0.10%, and the remainder is Fe and unavoidable impurities.

[0047] Step 2: The billet is heated to a uniform temperature of 1080-1150℃ for a heating time of t=(0.7-1.2)H, where H is the billet thickness. Then it is descaled by high-pressure water and rolled by a high-speed wire rod mill.

[0048] (1) The opening degree of the water tank before final rolling is ≥25%, and the water inflow into the water tank is ≥50m³. 3 / h, outlet water pressure ≥3.5 bar, final rolling temperature 860~880℃;

[0049] (2) The opening degree of the water tank after final rolling is ≤5%, the wire drawing temperature is 880~900℃, the temperature difference between the surface and core of the wire rod is ≤10℃, and the wire drawing speed is 30~35m / s.

[0050] Step 3: After spinning, the wire rod undergoes segmented controlled cooling on the Stellmore air-cooling line. The cooling rate is controlled by adjusting the fan operating value, the speed of the air-cooling roller conveyor, and the opening / closing of the insulation cover. The specific controlled cooling process is as follows:

[0051] (1) Speed ​​control requirements for air-cooled roller conveyor: The speed of the first section of roller conveyor is 0.56 m / s, and it is increased by 0.04 m / s for each subsequent section;

[0052] (2) Requirements for the opening degree of the fan, Jialing device and insulation cover: the opening degree of the front fan is ≥60%, the insulation cover is opened, the opening angle of the Jialing device is 3°, and the rapid cooling is 580~620℃, with the temperature difference between the surface and core of the wire rod ≤15℃; then the fan and insulation cover are turned off, and the cooling is carried out slowly at a cooling rate of 1~3℃ / s, with the winding temperature being 450~500℃.

[0053] (3) By matching the speed of the fan, the speed of the air-cooled roller, the Jialing device and the heat preservation cover of the Stellmore air-cooling line after rolling, the temperature is first rapidly cooled to 580-620℃ to suppress the formation of network cementite; then it is cooled at a cooling rate of 1-3℃ / s to complete the sorbite phase transformation and prevent the formation of abnormal martensite structure.

[0054] After the application of this invention, the product quality fully meets the relevant technical requirements and has been sent to users for further processing. Once the user's requirements are met, the annual production volume is expected to be about 20,000 tons. With a profit of 200 yuan per ton of steel, the economic benefit can reach 4 million yuan. It can be promoted and applied in the production of hot-rolled wire rod for high-strength prestressed steel strand and other high-carbon steels in various steel mills, and has good prospects for promotion and application.

[0055] The solution of this application will be described below through specific embodiments.

[0056] Example 1

[0057] A metal products company uses the technology of this invention to produce hot-rolled wire rods with a diameter of φ14mm and a diameter of 1×19S-21.8mm and a diameter of 1960MPa. The production process is as follows: converter smelting → LF refining → continuous casting → billet heating → high-speed wire rolling → wire drawing on a wire drawing machine → controlled cooling on a Steyrmo air-cooling line → coiling.

[0058] (1) A 200mm x 200mm billet was obtained by converter smelting, LF refining and continuous casting process. The smelting composition of the billet was C: 0.83%, Si: 0.50%, Mn: 0.65%, P: 0.011%, S: 0.009%, Cr: 0.25%, Cu: 0.05%, Ni: 0.03%, with the remainder being Fe and unavoidable impurities.

[0059] (2) Place the billet into a walking beam furnace for heating. The heating zone of the furnace is 1125℃ and the heating time is 200min.

[0060] (3) After descaling with high-pressure water, the wire rod is rolled into a φ14mm diameter round wire rod using a 30-stand high-speed wire rod mill. The wire rod is then spun into wire using a wire rod spinning machine. Before final rolling, the opening degrees of water tanks 1# to 4# are 25%, 28%, 28%, and 30%, respectively, and the water inflow rates are 50, 55, 55, and 55m³, respectively. 3 / h, outlet water pressure is 3.5 bar; temperature before final rolling is 860℃; water tank opening degree after final rolling is 3%, and wire drawing temperature is 880℃.

[0061] (4) The coiled wire after spinning is subjected to controlled cooling on the Stellmore air-cooling line. The specific control parameters are as follows: the roller speed of the first section is 0.56 m / s, the roller speed of the second section is 0.60 m / s, the roller speed of the third section is 0.64 m / s, the roller speed of the fourth section is 0.68 m / s, the roller speed of the fifth section is 0.72 m / s, the roller speed of the sixth section is 0.76 m / s, and the roller speed of the seventh section is 0.80 m / s. The speed of the 8th roller conveyor is 0.84 m / s, and the speed of the 9th to 13th roller conveyors is 0.88 m / s. The air volume of fans 1 to 6 on the air-cooled line is 100%, the air volume of fans 7 to 8 is 90%, the opening value of fan 9 is 70%, the opening value of fan 10 is 60%, and fans 11 to 14 are closed. The opening angle of the Jialing device is 3°. The insulation covers 1 to 20 are closed. The temperature entering the insulation cover is 580℃, and the winding temperature is 450℃.

[0062] (5) The φ14mm wire rod obtained by the above method has a tensile strength of 1250MPa, a reduction of area ≥38%, a sorbite content of 95%, no core martensite, and a grain boundary cementite grade of 0.5. The 1×19S-21.8mm prestressed steel strand made from the wire rod has a tensile strength of 1960MPa and a maximum force total elongation (L0≥500mm)Agt≥5.1%.

[0063] Example 2

[0064] A metal products company uses the technology of this invention to produce hot-rolled wire rods with a diameter of φ14mm and a diameter of 1×19S-21.8mm: 1960MPa steel strand. The production process is as follows: converter smelting → LF refining → continuous casting → billet heating → high-speed wire rolling → wire drawing on a wire drawing machine → controlled cooling on a Steyrmo air-cooling line → coiling.

[0065] (1) A 200mm×200mm billet was obtained by converter smelting, LF refining and continuous casting process. The smelting composition of the billet was C: 0.87%, Si: 0.60%, Mn: 0.80%, P: 0.013%, S: 0.008%, Cr: 0.35%, Cu: 0.02%, Ni: 0.03%, with the remainder being Fe and unavoidable impurities.

[0066] (2) Place the billet into a walking beam furnace for heating. The heating zone of the furnace is 1150°C and the heating time is 200 min.

[0067] (3) After descaling with high-pressure water, the wire rod is rolled into a φ14mm diameter round wire rod by a 30-stand high-speed wire rod mill. The wire rod is then spun into wire by a wire rod spinning machine. Before final rolling, the opening degrees of water tanks 1# to 4# are 25%, 28%, 28% and 30% respectively, and the water inflow rates of the water tanks are 50, 55, 55 and 55m³ respectively. 3 / h, outlet water pressure is 3.5 bar; temperature before final rolling is 880℃; water tank opening degree after final rolling is 3%, and wire drawing temperature is 900℃.

[0068] (4) The coiled wire after spinning is subjected to controlled cooling on the Stellmore air-cooling line. The specific control parameters are as follows: the roller speed of the first section is 0.56 m / s, the roller speed of the second section is 0.60 m / s, the roller speed of the third section is 0.64 m / s, the roller speed of the fourth section is 0.68 m / s, the roller speed of the fifth section is 0.72 m / s, the roller speed of the sixth section is 0.76 m / s, and the roller speed of the seventh section is 0.80 m / s. The speed of the 8th roller conveyor is 0.84 m / s, and the speed of the 9th to 13th roller conveyors is 0.88 m / s. The air volume of fans 1 to 6 on the air-cooled line is 100%, the air volume of fans 7 to 8 is 90%, the opening value of fan 9 is 70%, the opening value of fan 10 is 60%, and fans 11 to 14 are closed. The opening angle of the Jialing device is 3°. The insulation covers 1 to 20 are closed, the temperature entering the insulation cover is 620℃, and the winding temperature is 500℃.

[0069] (5) The φ14mm wire rod obtained by the above method has a tensile strength of 1310MPa, a reduction of area ≥35%, a sorbite content of 96%, no core martensite, and a grain boundary cementite grade of 1.0. The 1×19S-21.8mm prestressed steel strand made from the wire rod has a tensile strength of 2100MPa and a maximum force total elongation (L0≥500mm) Att≥4.5%.

[0070] Example 3

[0071] A metal products company uses the technology of this invention to produce hot-rolled wire rods with a diameter of φ14mm and a diameter of 1×19S-21.8mm: 1960MPa steel strand. The production process is as follows: converter smelting → LF refining → continuous casting → billet heating → high-speed wire rolling → wire drawing on a wire drawing machine → controlled cooling on a Steyrmo air-cooling line → coiling.

[0072] (1) A 200mm×200mm billet was obtained by converter smelting, LF refining and continuous casting process. The smelting composition of the billet was C: 0.85%, Si: 0.56%, Mn: 0.71%, P: 0.015%, S: 0.008%, Cr: 0.27%, Cu: 0.02%, Ni: 0.03%, and the remainder was Fe and unavoidable impurities.

[0073] (2) Place the billet into a walking beam furnace for heating. The heating temperature in the soaking zone of the furnace is 1080℃ and the heating time is 200min.

[0074] (3) After descaling with high-pressure water, the wire rod is rolled into a φ14mm diameter round wire rod by a 30-stand high-speed wire rod mill. The wire rod is then spun into wire by a wire rod spinning machine. Before final rolling, the opening degrees of water tanks 1# to 4# are 25%, 28%, 28% and 30% respectively, and the water inflow rates of the water tanks are 50, 55, 55 and 55m³ respectively. 3 / h, outlet water pressure is 3.5 bar; temperature before final rolling is 870℃; water tank opening degree after final rolling is 3%, and wire drawing temperature is 891℃.

[0075] (4) The coiled wire after spinning is subjected to controlled cooling on the Stellmore air-cooling line. The specific control parameters are as follows: the roller speed of the first section is 0.56 m / s, the roller speed of the second section is 0.60 m / s, the roller speed of the third section is 0.64 m / s, the roller speed of the fourth section is 0.68 m / s, the roller speed of the fifth section is 0.72 m / s, the roller speed of the sixth section is 0.76 m / s, and the roller speed of the seventh section is 0.80 m / s. The speed of the 8th roller conveyor is 0.84 m / s, and the speed of the 9th to 13th roller conveyors is 0.88 m / s. The air volume of fans 1 to 6 on the air-cooled line is 100%, the air volume of fans 7 to 8 is 90%, the opening value of fan 9 is 70%, the opening value of fan 10 is 60%, and fans 11 to 14 are closed. The opening angle of the Jialing device is 3°. The insulation covers 1 to 20 are closed. The temperature entering the insulation cover is 598℃, and the winding temperature is 482℃.

[0076] (5) The φ14mm wire rod obtained by the above method has a tensile strength of 1289MPa, a reduction of area ≥36%, a sorbite content of 96%, no core martensite, and a grain boundary cementite grade of 0.5. The 1×19S-21.8mm prestressed steel strand made from the wire rod has a tensile strength of 2080MPa and a maximum force total elongation (L0≥500mm)Agt≥4.6%.

[0077] After implementation, this invention has at least the following beneficial effects:

[0078] The high-speed wire rod rolling and controlled rolling-cooling processes, through precise control of the billet heating temperature and time, and strict control of the post-rolling wire drawing temperature, combined with advanced segmented controlled cooling technology, achieve comprehensive optimization of the hot-rolled wire rod production process. This series of precise process measures ensures that the final hot-rolled wire rod exhibits excellent performance in mechanical properties, dimensional accuracy, and surface quality, meeting the stringent requirements of high-end applications. This production method not only has a simple and clear process flow, facilitating operation and management, but also effectively reduces production costs and improves production efficiency. This makes the production technology for this high-quality hot-rolled wire rod easier to promote and apply in industrial production, which is of great significance for improving the overall production level and product quality of the industry.

[0079] The above are exemplary embodiments disclosed in this invention. The order of the disclosed embodiments is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. However, it should be noted that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the disclosed embodiments of this invention (including the claims) is limited to these examples. Various changes and modifications can be made without departing from the scope defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular.

[0080] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for preparing hot-rolled wire rod for prestressed steel strand, characterized in that, include: The required billet is obtained by sequentially smelting in a converter, refining in an LF furnace, and continuously casting. Then, the billet is heated, rolled in a high-speed wire rod, cooled in a Steyrmo air-cooling line, coiled and packaged to obtain hot-rolled wire rod for prestressed steel strand. Cooling is carried out in water tanks before and after the final rolling. The opening degree of the water tank before the final rolling is greater than that after the final rolling. In the controlled cooling process, the speed of the roller conveyor is gradually increased to a fixed value. In the high-speed wire rod rolling process, the billet homogenization temperature is 1080~1150℃, and the heating time is t=(0.7~1.2)H, where H is the billet thickness; Before final rolling, the water tank opening degree should be ≥25%, and the water inlet volume should be ≥50m³. 3 / h, outlet water pressure ≥3.5 bar, final rolling temperature 860~880℃; After final rolling, the water tank opening degree is ≤5%, and the wire drawing temperature is controlled at 880~900℃, with the temperature difference between the wire surface and the core being ≤10℃. The coiled wire after spinning is cooled in a controlled manner on the Stellmore air-cooling line. The initial speed of the roller conveyor is 0.50~0.60m / s, the speed of the roller conveyor in sections 2 to 8 increases by 0.03~0.05m / s each section, and the speed of the roller conveyor in sections 9 to 13 is 0.74~1.00m / s. In the controlled cooling process of the Stellmore air-cooled line, the opening degree of the front fan is ≥60%, the heat preservation cover is open, the opening angle of the Jialing device is 2°~4°, the rapid cooling is 580~620℃, and the temperature difference between the surface and core of the wire rod is ≤15℃.

2. The method for preparing hot-rolled wire rod for prestressed steel strand according to claim 1, characterized in that, The chemical composition of the hot-rolled wire rod for prestressed steel strand, by weight percentage, is as follows: C: 0.83%–0.87%, Si: 0.50%–0.60%, Mn: 0.60%–0.80%, P≤0.015%, S≤0.010%, Cr: 0.25%–0.35%, Cu≤0.20%, Ni≤0.10%; the remainder is Fe and unavoidable impurities.

3. The method for preparing hot-rolled wire rod for prestressed steel strand according to claim 1, characterized in that, The controlled cooling of the Stellmore air-cooled line also includes: turning off the fan and the insulation cover, and slowly cooling at a cooling rate of 1 to 3°C / s, with a winding temperature of 450 to 500°C.

4. A hot-rolled wire rod for prestressed steel strand, characterized in that, It is prepared by the method described in any one of claims 1-3 above.

5. The hot-rolled wire rod for prestressed steel strand according to claim 4, characterized in that, The hot-rolled wire rod used for the prestressed steel strand has a sorbite content of ≥95%, no core martensite, grain boundary cementite grade ≤1.0, tensile strength ≥1250MPa, and reduction of area ≥30%.

Images