Method for manufacturing high-carbon steel wire rod

Abstract

The present invention provides a high-carbon steel wire rod and a method for manufacturing the same. The manufacturing method includes the following steps. Molten steel is produced. A slab is obtained from the molten steel through a continuous casting process, and during the casting process, the slab is subjected to a rolling reduction treatment at a rolling reduction rate that first increases, then decreases, and then increases again. After heating the slab, it is subjected to block rolling to obtain a block material. After heating the block material, rolling and air cooling treatments are performed to obtain a wire rod. By precisely controlling the dynamic soft reduction parameters in the continuous casting process and performing a rolling reduction treatment on the slab at a rolling reduction rate that first increases, then decreases, and then increases again, the segregation and porosity problems in the center of the slab are significantly improved at the source.

Description

Technical Field

[0001] The present invention relates to the field of alloy technology, and specifically to high-carbon steel wire rods and a manufacturing method thereof.

Background Art

[0002] High-carbon steel wire rods are widely used in many industrial fields of the national economy, such as various steel cables, bridge cables, galvanized steel wires, and reinforcing materials for tires. Steel cord steel, which is an important classification of high-carbon steel, is mainly used as a skeleton material such as the radial cord of automobile tires. Especially in recent years, with the rise of new energy vehicles and the requirement of low carbon emissions, the high-strengthening of steel cords has become the main development direction. Improving the strength can not only reduce the usage amount of steel cords but also reduce the usage amount of rubber materials. Regarding the high-strengthening of steel cords, it is usually achieved by increasing the carbon content and adding trace alloying elements. As the carbon content increases, it becomes difficult to control the tissue characteristics of the wire rods, and especially the control of grain boundary cementite becomes a problem. Therefore, in order to reduce the influence of grain boundary cementite, it is necessary to consider the entire process from continuous casting to rolling.

Summary of the Invention

[0003] An object of the present invention is to provide a high-carbon steel wire rod and a manufacturing method thereof.

[0004] The present invention provides a manufacturing method of a high-carbon steel wire rod. In terms of mass percentage, the carbon content of the wire rod is ≧0.8%, and the manufacturing method includes a step of manufacturing molten steel, A step of obtaining a slab from the molten steel by a continuous casting process, wherein during the continuous casting process, soft reduction treatment is applied to the slab. When the central solid fraction fs of the slab satisfies 0.3 ≦ fs < 0.5, the slab is subjected to a rolling reduction treatment at a reduction rate of 3 to 5 mm / m to form negative segregation at the center of the slab. When the central solid fraction fs of the slab satisfies 0.5 ≦ fs < 0.8, the reduction rate is decreased, and the slab is subjected to a rolling reduction treatment at a reduction rate of 2 to 4 mm / m. When the central solid fraction fs of the slab satisfies 0.8 ≦ fs ≦ 1, the reduction rate is increased, and the slab is subjected to a rolling reduction treatment at a reduction rate of 4 to 6 mm / m. A step of heating the slab and then performing block rolling to obtain block materials, and A step of heating the block materials and then performing rolling and air cooling treatments to obtain the wire rods.

[0005] As a further improvement of the present invention, when the central solid fraction fs of the slab satisfies 0.3 ≦ fs < 0.5, subjecting the slab to a rolling reduction treatment at a reduction rate of 3 to 5 mm / m to form negative segregation at the center of the slab means When the central solid fraction fs of the slab satisfies 0.3 ≦ fs < 0.5, it includes subjecting the slab to a rolling reduction treatment in multiple stages within the range of a reduction rate of 3 to 5 mm / m, and the reduction rate gradually decreases.

[0006] As a further improvement of the present invention, the soft reduction treatment applied to the slab during the continuous casting process is Successively performing soft reduction treatment on the slab with 8 straightening machines in the horizontal part of the continuous casting machine. The 8 straightening machines are the No. 1 to No. 8 straightening machines respectively. When the central solid fraction fs of the slab satisfies 0.3 ≦ fs < 0.5, the slab is subjected to a rolling reduction treatment with the No. 1 to No. 3 straightening machines, and the reduction rates of the No. 1 to No. 3 straightening machines are controlled to gradually decrease. When the central solid fraction fs of the slab satisfies 0.5 ≦ fs < 0.8, the slab is subjected to a rolling reduction treatment with the No. 4 to No. 6 straightening machines. When the central solid fraction fs of the slab satisfies 0.8 ≦ fs ≦ 1, the slab is subjected to a rolling reduction treatment with the No. 7 and No. 8 straightening machines.

[0007] As a further improvement of the present invention, the reduction rate of the first leveler is controlled to be 4 - 5 mm / m, the reduction rate of the second leveler is controlled to be 3 - 5 mm / m, the reduction rate of the third leveler is controlled to be 3 - 4 mm / m, the reduction rate of the fourth to sixth levelers is controlled to be 2 - 3 mm / m, and the reduction rate of the seventh and eighth levelers is controlled to be 4 - 6 mm / m.

[0008] As a further improvement of the present invention, the step of obtaining a slab from the molten steel through a continuous casting process is as follows: Electromagnetically inductively heating the molten steel in a tundish and controlling the superheat degree to 10 - 20 °C. After the molten steel enters the mold from the tundish, electromagnetic stirring is performed, and the stirring current is controlled to be 400 - 600 A and the frequency is controlled to be 3 - 5 Hz.

[0009] As a further improvement of the present invention, the step of obtaining a slab from the molten steel through a continuous casting process is as follows: Continuous casting is carried out using a continuous casting machine with a cross-sectional dimension of 300 mm × 400 mm, the drawing speed is controlled to be 0.65 - 0.75 m / min, and the specific water volume in the secondary cooling zone of the continuous casting machine is controlled to be 0.15 - 0.25 L / kg.

[0010] As a further improvement of the present invention, after the step of obtaining a slab from the molten steel through a continuous casting process, It further includes the step of charging the slab into a soaking pit and keeping it warm for 72 hours or more in a state where the surface temperature of the slab is 800 °C or higher.

[0011] As a further improvement of the present invention, the step of heating the slab and then performing block rolling to obtain block materials is as follows: Heating the slab in a heating furnace, controlling the temperature in the soaking zone of the heating furnace to 1130 - 1180 °C, and controlling the residence time of the slab in the furnace to 240 - 300 min.

[0012] As a further improvement of the present invention, the step of heating the block materials and then performing rolling and air cooling treatment to obtain the wire rods is as follows: Before rolling, heat the block material in a heating furnace, control the soaking zone temperature of the heating furnace at 1080 - 1120 °C, control the inlet temperature of finish rolling of the block material at 860 - 890 °C, control the water tank pressure in the finish rolling mill at 3 - 4 bar, control the water flow rate at 1100 - 1200 m 3 / h, control the discharge temperature at 840 - 850 °C, and include rolling the block material into a wire rod with a diameter of 5.0 - 5.5 mm.

[0013] As a further improvement of the present invention, the step of obtaining the wire rod by heating the block material and then performing rolling and air cooling treatments is as follows: After rolling, operate the first to third blowers to cool the wire rod, and include controlling the air volume of the blowers at 30 - 100%.

[0014] As a further improvement of the present invention, the step of manufacturing molten steel includes: Manufacturing molten steel through the sequential steps of preliminary desulfurization of hot metal, steelmaking in a converter or an electric furnace, and LF refining process.

[0015] The present invention further provides a high - carbon steel wire rod. This high - carbon steel wire rod is manufactured by the above - mentioned high - carbon steel wire rod manufacturing method.

[0016] As a further improvement of the present invention, for the high - carbon steel wire rod, when the carbon content of the wire rod is 0.8 - 0.9% by mass percentage, under the YB - T4002 - 2013 standard, the evaluation of reticulated cementite in the wire rod is grade 0; when the carbon content of the wire rod is > 0.9%, under the YB - T4002 - 2013 standard, the evaluation of reticulated cementite in the wire rod is grade 1.

[0017] The beneficial effects of the present invention are as follows. The present invention precisely controls the dynamic soft reduction parameters during the continuous casting process, and within the range of solid - phase fraction of 0.3 - 1.0, by performing rolling reduction on the slab with a rolling reduction rate that is initially high, then low, and then high, the problems of segregation and density inhomogeneity from the source to the center of the slab are significantly improved. Furthermore, by combining with parameter control in subsequent block processing, rolling processing, and cooling processes, the reticulated cementite in the wire rod can be significantly reduced.

Brief Description of the Drawings

[0018]

Figure 1

Embodiments for Carrying out the Invention

[0019] To make the object, technical solution and advantages of the present invention clearer, hereinafter, with reference to the specific embodiments of the present invention and the corresponding drawings, the technical solution of the present invention will be clearly and completely described. It should be noted that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative labor are also included in the protection scope of the present invention.

[0020] Hereinafter, embodiments of the present invention will be described in detail. Examples of the embodiments are shown in the drawings, and the same or similar reference numerals represent the same or similar elements, or elements having the same or similar functions. The embodiments described below with reference to the drawings are exemplary and are for explaining the present invention, and should not be construed as limiting the present invention.

[0021] This embodiment provides a high-carbon steel wire rod and its manufacturing method. In this high-carbon steel wire rod, by mass percentage, the carbon content of the wire rod is ≧0.8%. The manufacturing method mainly controls the dynamic soft reduction parameters in the continuous casting process of a large cross-section slab to control the segregation index of the continuous casting slab (carbon content at the center of the slab / carbon content during melting) between 0.9 and 1.0, and further controls the parameters in the chunking process and the rolling process, thereby effectively reducing the network cementite at the center of the wire rod, and the manufactured steel wire rod is particularly suitable as steel for tire cords.

[0022] As shown in FIG. 1, the manufacturing method includes the following.

[0023] S1: Manufacture molten steel.

[0024] S2: Obtain a slab from the molten steel through a continuous casting process. During this process, perform soft reduction treatment on the slab. In the soft reduction treatment, when the central solid fraction fs of the slab satisfies 0.3 ≤ fs < 0.5, perform rolling reduction on the slab at a reduction rate of 3 - 5 mm / m; when the central solid fraction fs of the slab satisfies 0.5 ≤ fs < 0.8, reduce the reduction rate and perform rolling reduction on the slab at a reduction rate of 2 - 4 mm / m; when the central solid fraction fs of the slab satisfies 0.8 ≤ fs ≤ 1, increase the reduction rate and perform rolling reduction on the slab at a reduction rate of 4 - 6 mm / m.

[0025] S3: After heating the slab, perform block rolling to obtain block materials.

[0026] S4: After heating the block materials, perform rolling and air cooling treatments to obtain wire rods.

[0027] Step S1 includes preliminary desulfurization of hot metal, steelmaking in a converter or an electric furnace, and LF refining in sequence.

[0028] In the preliminary desulfurization process, mechanically stir the hot metal, blow in hydrated lime powder and fluorspar for desulfurization treatment of the hot metal, control the sulfur content in the hot metal, remove the desulfurization slag, and then charge the hot metal into the furnace for steelmaking.

[0029] In converter or electric furnace steelmaking, use the pre - desulfurized hot metal and scrap, etc. as raw materials for steelmaking to obtain molten steel. In the steelmaking process, blow oxygen into the hot metal for temperature - raising treatment, and then perform decarburization and dephosphorization treatments to obtain molten steel.

[0030] In the LF refining process, perform degassing treatment, alloying treatment, and temperature control on the molten steel to obtain molten steel with temperature and composition meeting the requirements.

[0031] Step S2 specifically includes the following.

[0032] S21: Heat the molten steel in the tundish. After the molten steel is distributed in the tundish, it enters the mold to form a solidification shell with a certain thickness. The slab with the solidification shell enters the secondary cooling zone under the traction of the straightening machine and undergoes spray water cooling.

[0033] Specifically, in this embodiment, the molten steel in the tundish is heated by electromagnetic induction, and the superheat degree is controlled to 10-20°C. After the molten steel enters the mold from the tundish, electromagnetic stirring is performed, and the stirring current is controlled to 400-600 A and the frequency is controlled to 3-5 Hz.

[0034] By electromagnetic induction heating in the tundish, the molten steel can be rotated, and the inclusions in the molten steel move toward the center direction under the drive of centrifugal force, collide and grow, and the speed of floating up to form slag is accelerated. When the refined molten steel enters the mold from the bottom of the tundish through the nozzle, the inclusions in the molten steel can be effectively reduced, and the segregation caused by the inclusion elements in the subsequent solidification process can be reduced. Electromagnetic stirring in the mold strengthens and promotes the convection, heat transfer and mass transfer processes of the molten steel in the liquid phase gap of the solidification shell, thereby controlling the solidification process of the slab, and is similarly effective in eliminating the superheat degree, improving the solidification structure and component segregation of the slab.

[0035] In this embodiment, continuous casting is carried out by a continuous casting machine with a cross-sectional dimension of 300 mm×400 mm to obtain a large cross-section slab. The casting speed is controlled to 0.65-0.75 m / min, and the specific water amount in the secondary cooling zone of the continuous casting machine is controlled to 0.15-0.25 L / kg.

[0036] S22: After the slab passes through the secondary cooling zone and the air cooling section, soft reduction treatment is sequentially performed by 8 straightening machines at the horizontal part of the continuous casting machine. The 8 straightening machines are machine No. 1 to machine No. 8 respectively. When the solid fraction fs at the center of the slab is 0.3≤fs<0.5, the reduction treatment of the slab is carried out by machine No. 1 to machine No. 3, and the reduction rates of machine No. 1 to machine No. 3 are controlled to decrease sequentially to form negative segregation at the center of the slab. When the solid fraction fs at the center of the slab is 0.5≤fs<0.8, the reduction treatment of the slab is carried out by machine No. 4 to machine No. 6. When the solid fraction fs at the center of the slab is 0.8≤fs≤1, the reduction treatment of the slab is carried out by machine No. 7 and machine No. 8.

[0037] During the casting process, when the liquid volume decreases due to the solidification shrinkage of the molten steel in the two-phase region at the solidification end, a local pressure drop is formed. Due to this pressure drop, the molten steel with concentrated segregation elements between dendrites near the center of the slab flows and accumulates and finally solidifies, forming center segregation. When the volume compensation is insufficient, it becomes center porosity. By means of the dynamic soft reduction technology, the fluidity and uniformity of the molten steel in the center can be effectively improved, the segregation and porosity caused by the cross-linking of dendrites during solidification can be reduced, and thereby the volume shrinkage due to the concentration of segregation elements during the solidification of the molten steel can be compensated.

[0038] Specifically, in this embodiment, when the solid fraction fs at the center of the slab satisfies 0 ≦ fs < 0.3, no soft reduction treatment is performed. Since the solidification shrinkage of the molten steel in this region can be compensated by the flow of the molten steel in front of it, the flow of the molten steel in this region does not cause the formation of center segregation. Instead, in order to homogenize the solute distribution in this region, no soft reduction treatment is performed at this time.

[0039] When the central solid fraction fs of the slab satisfies 0.3 ≤ fs < 0.5, the reduction ratio of the No. 1 leveler is controlled to be 4 - 5 mm / m, the reduction ratio of the No. 2 leveler is controlled to be 3 - 5 mm / m, and the reduction ratio of the No. 3 leveler is controlled to be 3 - 4 mm / m. At this time, the molten steel in the central part of the slab has good fluidity. A large reduction ratio causes the molten steel with a high solute concentration in the central part of the slab to flow in the direction opposite to the drawing direction at a high flow rate, resulting in the redistribution of solute elements in the molten steel and prone to causing negative segregation in the central part of the slab. Negative segregation refers to the segregation with a concentration lower than the average concentration of solutes in the alloy. First, a reduction treatment with a large reduction ratio is adopted. The molten steel in the central part of the slab is subjected to a large compressive force, causing the molten steel to flow from the center of the slab to one side. The solidification rate direction is from one side towards the center of the slab, and the two directions are opposite, making it easier to form negative segregation in the center of the slab. Also, due to the large reduction force, the dendrites near the center of the slab peel off along the reduction direction. The peeled dendrites flow into the central part of the slab together with the molten steel, becoming the center of nucleation in the central part of the slab. The central part solidifies first, and the solidification rate is from the central part of the slab towards one side, with the molten steel flow direction and the solidification rate direction being opposite, also making it easier to form negative segregation in the center of the slab. The formation of negative segregation can relatively clearly reduce the segregation situation in the central region of the slab. At the same time, to avoid cracks occurring inside the slab due to excessive reduction amount, the reduction ratio of the No. 1 leveler is controlled to be 4 - 5 mm / m, and the No. 2 and No. 3 levelers adopt a gradually decreasing reduction ratio.

[0040] When the central solid fraction fs of the slab satisfies 0.5 ≤ fs < 0.8, the reduction ratio of the No. 4 - No. 6 levelers is controlled to be 2 - 4 mm / m. By adopting a relatively small reduction ratio in this interval, the solidification shrinkage and thermal shrinkage amounts are compensated, and at the same time, it is avoided that the upstream molten steel flows in and forms segregation again.

[0041] When the central solid fraction of the slab satisfies 0.8 ≤ fs ≤ 1.0, the reduction ratio of the No. 7 and No. 8 levelers is controlled to be 4 - 6 mm / m. By adopting a large reduction ratio again at the end position of the solidification stage, the density of the central part of the slab is improved, achieving the effect of removing the central shrinkage hole and reducing the central point-like segregation.

[0042] In other embodiments of the present invention, the number of straightening machines and the specific reduction ratio of each straightening machine can also be adjusted according to factors such as the steel type and slab dimensions. However, it is a condition that the overall reduction ratio between the straightening machines is within a specified range and a gradient change curve that is initially high, then low, and then high again as described above can be formed.

[0043] S23: After obtaining a slab by continuous casting, it is charged into a soaking pit while its surface temperature is 800 °C or higher and soaked for 72 hours or more.

[0044] By slowly cooling the slab in the soaking pit, the temperature gradient on the surface layer of the slab can be effectively reduced, the increase in transformation stress can be prevented, the fine cracks and center segregation defects on the surface of the slab can be reduced, and furthermore, the quality of the slab can be improved.

[0045] In other embodiments of the present invention, the soaking time can also be specifically adjusted according to the dimensions of the slab.

[0046] As described above, by precisely controlling the reduction ratio in the dynamic soft reduction process, a gradient curve that is initially high, then low, and then high again is formed, effectively reducing the segregation and porosity problems in the center of the slab. Samples were taken from the slab, and based on YB-T4002-2013 "Macrostructure Defect Evaluation Diagram of Continuously Cast Steel Bloom", the macro intermediate cracks of the slab were evaluated, and the segregation value in the center of the slab was analyzed by drilling analysis. As a result, the segregation index of the slab produced by this implementation method can be controlled to 0.9 - 1.0, and the center porosity level can be controlled to below grade 0.5.

[0047] Step S3 includes heating the slab in a heating furnace, controlling the soaking zone temperature of the heating furnace to 1130 - 1180 °C, and controlling the residence time of the slab in the furnace to 240 - 300 min.

[0048] Step S4 After maintaining and flaw-detecting the block materials, load them into a heating furnace for heating, and control the soaking zone temperature of the heating furnace at 1080 - 1120 °C. Control the temperature of the block materials at the entrance of finish rolling at 860 - 890 °C, control the water tank pressure in the finish rolling mill at 3 - 4 bar, control the water flow rate at 1100 - 1200 m 3 / h, and control the discharge temperature at 840 - 850 °C to roll the block materials into wire rods with a diameter of 5.0 - 5.5 mm.

[0049] After rolling, start the first to third blowers to cool the wire rods, and control the air volume of the blowers at 30 - 100%.

[0050] In steps S3 and S4, adjust and control the temperature parameters in the processes of blocking and rolling, and gradually reduce the temperature of the rolled material, so as to increase the accumulated deformation energy of the rolled material, refine the austenite crystal grain size of the rolled material, and further increase the proportion of the grain boundaries of the tissue crystal grains in the rolled material. This adjusts the conditions for controlling the precipitation of network carbides in the wire rods, and finally effectively reduces the amount of network carbides in the center of the wire rods, improving the tissue uniformity of the wire rods. Compared with the existing processes, this method can effectively control the formation of network carbides without the need to set a higher temperature than the normal process in the rolling and cooling processes by controlling the central segregation in the continuous casting process.

[0051] In this embodiment, a high-carbon steel wire rod manufactured by the above-mentioned method for manufacturing a high-carbon steel wire rod is also provided.

[0052] In terms of mass percentage, when the carbon content of the wire rod is 0.8 - 0.9%, in accordance with the YB-T4002-2013 standard, the evaluation of the network carbides in the wire rod is grade 0; when the carbon content of the wire rod is >0.9%, in accordance with the YB-T4002-2013 standard, the evaluation of the network carbides in the wire rod is grade 1.

[0053] When the wire rod is processed into a steel cord with a diameter of 0.15 - 0.25 mm, the wire breakage rate is 2 - 3 times / ton, and the wire breakage rate is reduced by more than 20% compared with the existing wire rods.

[0054] As described above, in this embodiment, the dynamic soft reduction parameters in the continuous casting process are precisely controlled, and within the range of a solid fraction of 0.3 to 1.0, the slab is subjected to a rolling reduction treatment at a rolling reduction rate that is initially high, then low, and then high again, thereby significantly improving the problems of segregation and porosity in the center of the slab. Furthermore, by combining with parameter control in subsequent block processing, rolling processing, and cooling processes, the network carbide in the wire rod is significantly reduced.

[0055] Hereinafter, specific embodiments of the present invention will be further described with reference to six examples.

[0056] Examples 1 to 6 were manufactured according to the following procedure.

[0057] After obtaining the molten steel, the ladle is lifted to the continuous casting platform for protective casting. The C content of the steel grades in Examples 1 to 6 is as shown in Table 1.

[0058]

Table 1

[0059] After the molten steel forms a cast shell of a certain thickness in the mold, it proceeds to the spray cooling in the secondary cooling zone under the traction action of the straightening machine. The drawing speed of the continuous caster, the tundish superheat, the mold electromagnetic stirring parameters, and the unit water volume in the secondary cooling zone are as shown in Table 2.

[0060]

Table 2

[0061] The slab passes through the secondary cooling zone and the air cooling section and then enters the soft reduction section for rolling reduction treatment. The solid fraction at the center of the slab corresponding to each straightening machine is as shown in Table 3, and the rolling reduction rate used in each straightening machine is as shown in Table 4.

[0062]

Table 3

[0063]

Table 4

[0064] After the slab exits the line, it is lifted and transported to the soaking pit for pit cooling. The surface temperature at the pit entrance and the pit cooling time are as shown in Table 5.

[0065]

Table 5

[0066] Macrostructure samples were taken from the slab, and the macro intermediate cracks of the slab were evaluated based on YB-T4002-2013 "Evaluation Diagram of Macrostructure Defects of Continuously Cast Steel Blooms". In addition, the segregation value at the center of the slab was analyzed by drilling analysis. The results are as shown in Table 6.

[0067]

Table 6

[0068] After the slab exits the pit, it is lifted and transported to the block-making factory and charged into the heating furnace. The furnace temperature in the soaking zone of the heating furnace and the residence time in the furnace are as shown in Table 7, and the dimensions of the block-making material are 140mm×140mm.

[0069]

Table 7

[0070] After cleaning and flaw detection of the block-making material, it is lifted and transported to the rolling factory and charged into the heating furnace. The rolling process parameters are as shown in Table 8.

[0071]

Table 8

[0072] Samples were taken from the wire rod, corrosion treatment was carried out with a nitric acid alcohol corrosion solution, and the metal structure of the wire rod was observed. The results are as shown in Table 9.

[0073]

Table 9

[0074] Steel cords with different diameters were manufactured from the wire rod, and the results of the fracture rate are as shown in Table 10.

[0075]

Table 10

[0076] Although this specification has been described according to embodiments, each embodiment does not only include one independent technical solution, and the description method like this specification is only for clarification. Those skilled in the art should regard this specification as a whole, and by appropriately combining the technical solutions in each embodiment, other embodiments understandable by those skilled in the art can be formed.

[0077] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and are not for limiting the protection scope of the present invention. Any equivalent embodiments or modifications made without departing from the technical spirit of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for manufacturing a high-carbon steel wire rod with a carbon content of 0.8% or more by mass percentage, comprising: a step of manufacturing molten steel; a step of obtaining a slab from the molten steel by a continuous casting process, wherein the slab is subjected to soft reduction during this process. The soft reduction is carried out as follows: when the solid fraction fs at the center of the slab satisfies 0.3 ≤ fs < 0.5, the slab is subjected to a rolling reduction with a reduction rate of 3 to 5 mm / m to form negative segregation at the center of the slab; when the solid fraction fs at the center of the slab satisfies 0.5 ≤ fs < 0.8, the reduction rate is decreased and the slab is subjected to a rolling reduction with a reduction rate of 2 to 3 mm / m; when the solid fraction fs at the center of the slab satisfies 0.8 ≤ fs ≤ 1, the reduction rate is increased and the slab is subjected to a rolling reduction with a reduction rate of 4 to 6 mm / m; a step of heating the slab and then performing block rolling to obtain block materials; and a step of heating the block materials and then performing rolling and air cooling to obtain the wire rod. A method for manufacturing a high-carbon steel wire rod, characterized by comprising the above steps.

2. When the solid fraction fs at the center of the slab satisfies 0.3 ≤ fs < 0.5, the step of subjecting the slab to a rolling reduction with a reduction rate of 3 to 5 mm / m to form negative segregation at the center of the slab includes: When the solid fraction fs at the center of the slab satisfies 0.3 ≤ fs < 0.5, within the range of a reduction rate of 3 to 5 mm / m, the slab is subjected to a multi-stage rolling reduction with a gradually decreasing reduction rate to form negative segregation at the center of the slab. The method for manufacturing a high-carbon steel wire rod according to Claim 1, characterized by including the above step.

3. The soft reduction applied to the slab during the continuous casting process is: In the horizontal part of the continuous casting machine, the slab is sequentially passed through 8 straightening machines for soft reduction. The 8 straightening machines are the No. 1 to No. 8 straightening machines. When the solid fraction fs at the center of the slab satisfies 0.3 ≤ fs < 0.5, the slab is subjected to a rolling reduction by the No. 1 to No. 3 straightening machines, and the reduction rates of the No. 1 to No. 3 straightening machines are gradually decreased. When the solid fraction fs at the center of the slab satisfies 0.5 ≤ fs < 0.8, the slab is subjected to a rolling reduction by the No. 4 to No. 6 straightening machines. When the solid fraction fs at the center of the slab satisfies 0.8 ≤ fs ≤ 1, the slab is subjected to a rolling reduction by the No. 7 and No. 8 straightening machines. The method for manufacturing a high-carbon steel wire rod according to Claim 2, characterized by including the above step.

4. Control the reduction rate of the No. 1 straightening machine to 4 - 5 mm / m, the reduction rate of the No. 2 straightening machine to 3 - 5 mm / m, the reduction rate of the No. 3 straightening machine to 3 - 4 mm / m, the reduction rate of the No. 4 - No. 6 straightening machines to 2 - 3 mm / m, and the reduction rate of the No. 7 and No. 8 straightening machines to 4 - 6 mm / m. The method for manufacturing a high-carbon steel wire rod according to claim 3, characterized in that.

5. The step of obtaining a slab from the molten steel by a continuous casting process is Electromagnetically inductively heat the molten steel in the tundish, control the superheat degree to 10 - 20 °C, and after the molten steel enters the mold from the tundish, perform electromagnetic stirring, and control the stirring current to 400 - 600 A and the frequency to 3 - 5 Hz. The method for manufacturing a high-carbon steel wire rod according to claim 1, characterized in that it includes.

6. The step of obtaining a slab from the molten steel by a continuous casting process is Perform continuous casting with a continuous casting machine having a cross-sectional dimension of 300 mm × 400 mm, control the drawing speed to 0.65 - 0.75 m / min, and control the specific water volume in the secondary cooling zone of the continuous casting machine to 0.15 - 0.25 L / kg. The method for manufacturing a high-carbon steel wire rod according to claim 1, characterized in that it includes.

7. After the step of obtaining a slab from the molten steel by a continuous casting process, It further includes a step of charging into a holding pit and holding for 72 hours or more in a state where the surface temperature is 800 °C or higher. The method for manufacturing a high-carbon steel wire rod according to claim 1, characterized in that.

8. The step of heating the slab and then performing block rolling to obtain a block material is Heat the slab in a heating furnace, control the soaking zone temperature of the heating furnace to 1130 - 1180 °C, and control the residence time of the slab in the furnace to 240 - 300 min. The method for manufacturing a high-carbon steel wire rod according to claim 1, characterized in that it includes.

9. The step of heating the block material and then performing rolling and air cooling treatment to obtain the wire rod is Before rolling, heat the divided block material in a heating furnace, control the soaking zone temperature of the heating furnace to 1080 - 1120 °C, control the entry temperature of the divided block material into finish rolling to 860 - 890 °C, control the water tank pressure in the finish rolling mill to 3 - 4 bar, control the water flow rate to 1100 - 1200 m ３ / h, control the discharge temperature to 840 - 850 °C, and roll the divided block material into a wire rod with a diameter of 5.0 - 5.5 mm. The method for manufacturing a high-carbon steel wire rod according to claim 1, characterized by comprising the above.

10. The step of heating the block material and then performing rolling and air cooling treatment to obtain the wire rod is After rolling, operate the No. 1 - No. 3 blowers to cool the wire rod, and control the air volume of the blowers to 30 - 100%. The method for manufacturing a high-carbon steel wire rod according to claim 9, characterized in that it includes.

11. The step of manufacturing the molten steel is It includes manufacturing the molten steel by sequentially passing through preliminary desulfurization of hot metal, converter or electric furnace steelmaking, and LF refining process. The method for manufacturing a high-carbon steel wire rod according to claim 1, characterized in that.

12. The high-carbon steel wire rod manufactured by the method for manufacturing a high-carbon steel wire rod according to any one of claims 1 to 11.

13. When the carbon content of the wire rod is 0.8 to 0.9% by mass percentage, in accordance with the YB-T 4002-2013 standard, the evaluation grade of the network carbide in the wire rod is grade 0, When the carbon content of the wire rod exceeds 0.9%, in accordance with the YB-T 4002-2013 standard, the evaluation grade of the network carbide in the wire rod is grade 1, The high-carbon steel wire rod according to claim 12, characterized by this.

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