A wire rod for fine steel cord, steel wire, cord and manufacturing method thereof

Abstract

The application belongs to the technical field of wire rod production method, and particularly relates to a wire rod for fine steel wire cord, steel wire, cord and a manufacturing method thereof. The chemical composition of the wire rod comprises, in percentage by mass, C: 0.79-0.84%, Si: 0.15-0.30%, Mn: 0.45-0.55%, P≤0.015%, S: 0.0030-0.010%, total oxygen: 0.0008-0.0022%, Als: 0.0002-0.0012%, Mg: 0.0002-0.0012%, Nb: 0.0003-0.0009%, Mo: 0.0003-0.0012%, and the balance of Fe and inevitable impurities. The application makes the cross-section hardness distribution of the wire rod and the steel wire uniform through chemical composition and production process design, and meets the plying performance requirement of the user in the process of processing the fine steel wire cord from the wire rod.

Description

Technical Field

[0001] This invention belongs to the technical field of wire rod production methods, specifically relating to a wire rod, steel wire, cord, and manufacturing method for fine steel wire cord. Background Technology

[0002] Cord steel wire rods are used in the production of tire steel cords. During user processing, the wire rods undergo drawing and stranding processes, thus users have strict requirements for their processing performance. The hardness distribution of the wire rod's structure is a crucial indicator affecting its processing performance. The hardness of the wire rod's structure is a comprehensive reflection of its chemical composition and microstructure; variations in hardness within the wire rod's cross-section directly reflect its ability to deform uniformly within that cross-section. A more uniform hardness distribution within the wire rod's cross-section improves the uniformity of hardness within the steel wire's cross-section, thereby enhancing the stranding performance of the steel wire and creating conditions for manufacturing fine steel cords with complex and demanding structures.

[0003] Patent CN201910638740.0 discloses an ultra-fine, ultra-high-strength steel wire, a wire rod for ultra-fine, ultra-high-strength steel wire, and a method for producing the same. The chemical composition of the wire rod for ultra-fine, ultra-high-strength steel wire, by mass percentage, includes: C 0.90%–0.96%, Si 0.12%–0.30%, Mn 0.30%–0.65%, Cr 0.10%–0.30%, Al ≤ 0.004%, Ti ≤ 0.001%, Cu ≤ 0.01%, Ni ≤ 0.01%, S ≤ 0.01%, P ≤ 0.01%, O ≤ 0.0006%, N ≤ 0.0006%, with the remainder being Fe and unavoidable impurity elements. The inclusion size is ≤ 4 μm, and the average density of brittle inclusions is ≤ 2 inclusions / mm². 2 The aforementioned wire rod for ultra-fine, ultra-high-strength steel wire can be used as a base material for producing ultra-fine, ultra-high-strength steel wire with a diameter of 50-60 μm and a tensile strength ≥4500 MPa. Furthermore, it can achieve a continuous wire drawing distance of ≥300 km during the process of producing ultra-fine, ultra-high-strength steel wire. The production method includes vacuum induction melting, remelting, forging, and rolling. This patent focuses on ultra-fine, ultra-high-strength steel wire, the wire rod for ultra-fine, ultra-high-strength steel wire, and their production methods. While the wire rod is applied to the production of ultra-fine steel wire, the stranding properties of the steel wire are not mentioned, nor is the cross-sectional hardness distribution of the wire rod and the steel wire described.

[0004] To meet users' requirements for the processing performance of wire rods used in precision steel wire cords, especially the requirements for the stranding performance of wire rods, there is an urgent need to develop high-quality wire rods for precision steel wire cords. These rods should have a uniform hardness distribution across their cross-section, ensuring that the wires made from the wire rods also have a uniform hardness distribution across their cross-section, thus laying the foundation for improving the stranding performance of the wires. Summary of the Invention

[0005] The purpose of this invention is to provide a wire rod, steel wire, and cord for fine steel wire cord, and a method for manufacturing the same. Through the design of chemical composition and production process, the hardness distribution of the wire rod and steel wire cross-section is made uniform, which meets the user's requirements for the stranding performance in the process of processing wire rod into fine steel wire cord.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] The first aspect of this invention provides a wire rod for fine steel wire cord, wherein the chemical composition of the wire rod comprises, by mass percentage:

[0008] C: 0.79%–0.84%, Si: 0.15%–0.30%, Mn: 0.45%–0.55%, P≤0.015%, S: 0.0030%–0.010%, total oxygen: 0.0008%–0.0022%, Als: 0.0002%–0.0012%, Mg: 0.0002%–0.0012%, Nb: 0.0003%–0.0009%, Mo: 0.0003%–0.0012%, balance being Fe and unavoidable impurities.

[0009] In the above technical solution, the ferrite Si content in the pearlite structure of the wire rod is further 0.15% to 0.45%.

[0010] The selection principles and content design reasons for each chemical component in this invention are as follows:

[0011] C: Carbon is the main element controlling the strength of steel wire. If the carbon content of the steel wire is too low, it will not meet the user's strength requirements, while if the content is too high, the strength of the steel wire will exceed the user's requirements. At the same time, a higher carbon content will increase the wire breakage rate during the drawing process, and increase the user's scrap rate. Therefore, in this invention, the carbon content is controlled at 0.79% to 0.84%.

[0012] Si: Silicon is the main deoxidizing element in high-carbon steel. Low silicon content will result in insufficient deoxidation of the molten steel; excessive silicon content will cause large silicate inclusions in the steel, reducing the drawing performance of the steel wire. Silicon dissolves into ferrite, increasing the hardness of ferrite, reducing the hardness difference between ferrite and cementite, and improving the uniformity of hardness in the steel wire structure. Therefore, the silicon content in this invention is controlled at 0.15% to 0.30%.

[0013] Mn: Manganese is an element that improves the strength of wire, enabling steel wire to meet the tensile strength requirements of users. Manganese also lowers the eutectoid transformation temperature of steel, refines the pearlite structure of the steel wire, and improves the deep processing capability of the steel wire. Therefore, the manganese content in this invention is controlled at 0.45% to 0.55%.

[0014] P: Phosphorus tends to form banded segregation in wire rods, reducing the machinability of the steel wire. Therefore, in this invention, the silicon and phosphorus content is controlled at ≤0.015%.

[0015] S: High sulfur content in steel reduces the cold working properties of steel wire. Since MnS inclusions have good deformability, an appropriate amount of sulfur in the steel can reduce the harmful effects of non-deformable inclusions and prevent the formation of microcracks caused by these inclusions. Therefore, in this invention, the sulfur content is controlled between 0.0030% and 0.010%.

[0016] Total oxygen content: When the oxygen content is high, the inclusions in the steel are large in size and numerous, which easily leads to the appearance of micro-cracks during the machining process of the steel wire, causing the steel wire to crack. When the oxygen content is low, the inclusions in the steel wire have poor deformation ability, making it easy for micro-cracks to appear between the inclusions and the steel wire matrix, which is not conducive to improving the machinability of the steel wire; therefore, in this invention, the total oxygen content of the steel wire is controlled at 0.0008% to 0.0022%.

[0017] Als: When the acid-soluble aluminum content is high, the size of Al2O3 inclusions in the steel increases, making the steel wire more prone to cracking during processing. When the acid-soluble aluminum content in the wire rod is too low, the melting point of the inclusions in the steel is high, the deformation capacity of the inclusions decreases, the local stress of the steel wire increases during processing, and the steel wire is prone to micro-cracks, leading to cracking and breakage. Therefore, the acid-soluble aluminum content in this invention is controlled at 0.0002% to 0.0012%.

[0018] Mg: Magnesium controls the oxygen content in steel and also the type of inclusions. Higher magnesium content leads to the formation of magnesium-aluminum spinel inclusions, reducing the machinability of the steel wire. Appropriate magnesium content improves the deformability of inclusions, expands the area of ​​high deformability of inclusions, and is beneficial to improving the deformability of the steel wire. Therefore, in this invention, the magnesium content is controlled between 0.0002% and 0.0012%.

[0019] Niobium (Nb) can inhibit grain growth in steel billets during heating, thereby improving the uniformity of hardness in the steel wire structure. However, excessively high niobium content in steel leads to significant work hardening during deformation, reducing the wire rod's deep processing capability. Therefore, the niobium content in this invention is controlled at 0.0003% to 0.0009%.

[0020] Mo: Molybdenum is a strong carbide-forming element. The dispersed distribution of molybdenum carbides refines the grain size of steel wire and improves the uniformity of hardness distribution across the wire cross-section. However, excessively high molybdenum content in steel reduces the machinability of the wire rod. Therefore, this invention controls the molybdenum content to be between 0.0003% and 0.0012%.

[0021] A second aspect of the present invention provides a method for manufacturing the above-mentioned fine steel wire cord coils, the method comprising the following steps:

[0022] (1) Continuous casting: The molten steel is continuously cast. The cross-sectional dimensions of the continuously cast billet are (250~300)mm*(350~400)mm. The grain size on the surface of the continuously cast billet is 260~520μm, and the grain size in the core of the continuously cast billet is 800~1100μm. The carbon segregation index at the 1 / 2 thickness position on the center line of the cross-sectional length of the continuously cast billet is controlled at 0.95~1.07, the carbon segregation index at the 1 / 4 thickness position on the center line of the cross-sectional length of the continuously cast billet is controlled at 0.96~1.06, and the carbon segregation index at the surface position on the center line of the cross-sectional length of the continuously cast billet is controlled at 0.94~1.0.

[0023] (2) Heating and rolling: The continuously cast billet is hot-charged, with a total furnace time of 3.8 to 4.5 hours, a soaking zone temperature of 1230 to 1280°C, and a soaking zone holding time of 40 to 60 minutes. After heating, the continuously cast billet is continuously rolled into a square billet with a final rolling temperature of 940 to 1050°C. The cross-sectional dimensions of the square billet are (140 to 180) mm * (140 to 180) mm.

[0024] (3) Wire rod rolling: The total time of the billet in the furnace is 150-170 min, the temperature of the soaking zone is 1130-1170℃, and the holding time of the soaking zone is 30-50 min. Through high-temperature diffusion of the billet, the segregation of elements such as carbon and manganese is reduced, and the grain size of the billet is controlled. After the billet is heated, it is rolled into wire rod after rough rolling, intermediate rolling, pre-finish rolling, finish rolling and double module rolling. The wire rod rolling specification is 5.0-6.0 mm.

[0025] (4) Wire rod cooling: After wire drawing, the wire rod is cooled on the air-cooled roller conveyor. The temperature at which cementite begins to precipitate is controlled at 740-770℃, and the pearlite phase transformation supercooling is controlled at 100-150℃. When the phase transformation time on the air-cooled line is 4-6s, the pearlite content of the wire rod is ≥50%. When the phase transformation time is 14-16s, the pearlite content is ≥95%. The wire rod after cooling is mainly composed of sorbite structure, which is beneficial for the user to draw steel wire.

[0026] In the above technical solution, further, in step (1), the molten steel is molten iron and scrap steel, wherein the scrap steel accounts for 5% to 10% of the mass of the molten steel.

[0027] In the above technical solution, further, in step (1), after the molten steel is smelted in the converter, it is refined in an LF furnace. The refining time of the LF furnace is 30 to 50 minutes, the refining temperature is 1450 to 1550°C, and argon gas is used for stirring during the molten steel refining process. The argon gas flow rate is 200 to 500 NL / min.

[0028] In the above technical solution, further, in step (3), the pre-finishing rolling temperature of the rolled piece is 950~1000℃, and the temperature compensation deformation rate factor of the last pass of the pre-finishing rolling is (1.1~2.6)*10. 13 s -1 The temperature at which the workpiece enters the finishing mill is 880–960℃, and the temperature compensation deformation rate factor for the final pass of finishing milling is (1.6–3.2)*10. 14 s -1 The temperature of the double-module entry is 890–940℃, and the temperature compensation deformation rate factor for the last pass of the double-module rolling mill is (4.5–9.9)*10. 14 s -1 .

[0029] In the above technical solution, further, in step (3), the wire rod spinning temperature is 910-940℃. By using a higher wire rod spinning temperature, the cooling speed of the wire rod on the air-cooled roller conveyor is increased, laying the foundation for controlling the final structure of the wire rod.

[0030] A third aspect of the present invention provides a fine steel wire, said steel wire being manufactured from the aforementioned wire rod.

[0031] A fourth aspect of the present invention provides a method for manufacturing the above-mentioned fine steel wire, comprising the following steps:

[0032] a. Mechanical descaling: The wire rod undergoes mechanical descaling treatment, and the residual iron oxide scale on the surface of the wire rod is ≤0.07%;

[0033] b. Wire rod drawing: Wire rod is drawn in multiple passes to produce intermediate wires with a diameter of 0.8 to 1.2 mm;

[0034] c. Heat treatment of intermediate wire: After heating the intermediate wire to 880-915℃, it undergoes a phase change at 555-575℃ after cooling.

[0035] d. Wire drawing: The heat-treated intermediate wire is drawn into a steel wire with a diameter of 0.15 to 0.20 mm.

[0036] A fifth aspect of the present invention provides a fine cord made of the aforementioned steel wire.

[0037] The beneficial effects of this invention are as follows:

[0038] This invention, through chemical composition and production process design, ensures uniform hardness distribution across the cross-section of wire rod and steel wire, meeting users' requirements for the stranding performance in the process of processing wire rod into fine steel wire cord. The hardness difference at different parts of the cross-section of 5.5mm diameter wire rod is controlled within 35HV, and the hardness difference across the cross-section of 0.175mm diameter steel wire is controlled within 10HV, meeting users' quality requirements for the production of steel wire and steel wire cord. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the hardness test of the wire rod cross section;

[0040] Figure 2 This is a schematic diagram of a steel wire cross-section hardness test. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, 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 effort are within the scope of protection of the present invention.

[0042] The chemical composition of the wire rods in Examples 1-6 of this invention is shown in Table 1.

[0043] Table 1 Chemical composition of wire rod

[0044]

[0045] The manufacturing method of the above-mentioned fine steel wire cord coils includes the following steps:

[0046] (1) Smelting: The molten steel is made of molten iron and scrap steel, of which scrap steel accounts for 5% to 10% of the mass of the molten steel. After the molten steel is smelted in a converter, it is refined by LF furnace. The LF furnace refining time is 30 to 50 minutes and the refining temperature is 1450 to 1550℃. Argon gas is used for stirring during the molten steel refining process. The argon gas flow rate is 200 to 500 NL / min.

[0047] Table 2 Smelting process parameters

[0048] Example LF furnace refining time, min Refining temperature, °C Argon flow rate NL / min 1 35 1512 300 2 49 1531 250 3 42 1532 350 4 38 1509 400 5 45 1523 300 6 41 1541 350

[0049] (2) Continuous casting: The molten steel is continuously cast. The cross-sectional dimensions of the continuously cast billet are (250~300)mm*(350~400)mm. The grain size on the surface of the continuously cast billet is 260~520μm, and the grain size in the core of the continuously cast billet is 800~1100μm. The carbon segregation index at the 1 / 2 thickness position on the center line of the cross-sectional length of the continuously cast billet is controlled at 0.95~1.07, the carbon segregation index at the 1 / 4 thickness position on the center line of the cross-sectional length of the continuously cast billet is controlled at 0.96~1.06, and the carbon segregation index at the surface position on the center line of the cross-sectional length of the continuously cast billet is controlled at 0.94~1.0.

[0050] Table 3 Continuous Casting Process Parameters

[0051]

[0052]

[0053] (3) Heating and rolling: The continuous casting billet is hot-charged, with a total furnace time of 3.8 to 4.5 hours, a soaking zone temperature of 1230 to 1280°C, and a soaking zone holding time of 40 to 60 minutes. After heating, the continuous casting billet is continuously rolled into a square billet with a final rolling temperature of 940 to 1050°C. The cross-sectional dimensions of the square billet are (140 to 180) mm * (140 to 180) mm.

[0054] Table 4 Heating and Rolling Process Parameters

[0055]

[0056] (4) Wire rod rolling: The total furnace time for the billet is 150-170 min, the soaking zone temperature is 1130-1170℃, and the soaking zone holding time is 30-50 min. Through high-temperature diffusion of the billet, the segregation of elements such as carbon and manganese is reduced, and the grain size of the billet is controlled. After heating, the billet undergoes roughing, intermediate rolling, pre-finishing rolling, finishing rolling, and double-module rolling. The pre-finishing rolling temperature of the rolled piece is 950-1000℃, and the temperature compensation deformation rate factor for the last pass of the pre-finishing rolling is (1.1-2.6)*10. 13 s -1 The temperature at which the workpiece enters the finishing mill is 880–960℃, and the temperature compensation deformation rate factor for the final pass of finishing milling is (1.6–3.2)*10. 14 s -1 The temperature of the double-module entry is 890–940℃, and the temperature compensation deformation rate factor for the last pass of the double-module rolling mill is (4.5–9.9)*10. 14 s -1 Then, the wire rod is spun into coils at a temperature of 910–940°C. The higher coiling temperature increases the cooling rate of the wire rod on the air-cooled roller conveyor, laying the foundation for controlling the final structure of the wire rod. The wire rod is rolled to a diameter of 5.0–6.0 mm.

[0057] Table 5. Parameters for Wire Rod Rolling

[0058]

[0059]

[0060] Table 6. Parameters for Wire Rod Spinning Process

[0061] Example Wire rod spinning temperature, °C Wire rod specifications, mm 1 937 5.5 2 925 5.5 3 922 5.5 4 921 5.5 5 915 5.5 6 916 5.5

[0062] (5) Wire rod cooling: After wire drawing, the wire rod is cooled on the air-cooled roller conveyor. The temperature at which cementite begins to precipitate is controlled at 740-770℃, and the pearlite phase transformation supercooling is controlled at 100-150℃. When the phase transformation time on the air-cooled line is 4-6s, the pearlite content of the wire rod is ≥50%. When the phase transformation time is 14-16s, the pearlite content is ≥95%. The wire rod after cooling is mainly composed of sorbite structure, which is beneficial for the user to draw steel wire.

[0063] Table 7. Wire Rod Cooling Process Parameters

[0064]

[0065] The method for manufacturing steel wire using the above-mentioned coiled wire includes the following steps:

[0066] a. Mechanical descaling: The wire rod undergoes mechanical descaling treatment, and the residual iron oxide scale on the surface of the wire rod is ≤0.07%;

[0067] b. Wire rod drawing: Wire rod is drawn in multiple passes to produce intermediate wires with a diameter of 0.8 to 1.2 mm;

[0068] c. Heat treatment of intermediate wire: After heating the intermediate wire to 880-915℃, it undergoes a phase change at 555-575℃ after cooling.

[0069] d. Wire drawing: The heat-treated intermediate wire is drawn into a steel wire with a diameter of 0.15 to 0.20 mm.

[0070] Table 8 Steel Wire Manufacturing Process Parameters

[0071] Example Intermediate wire diameter, mm Steel wire heating temperature, ℃ Phase transition temperature, °C Final wire diameter, mm 1 1.0 903 562 0.175 2 1.0 902 568 0.175 3 1.0 905 571 0.175 4 1.0 902 567 0.175 5 1.0 901 563 0.175 6 1.0 902 559 0.175

[0072] Hardness tests were performed on the wire rods and steel wires from Examples 1-6 above;

[0073] Wire rod hardness testing method: Divide the cross-section of the wire rod into 5 equal parts by radius, and test the hardness at 6 points from the surface to the core. Then analyze the hardness difference across the cross-section. See the schematic diagram. Figure 1 .

[0074] Steel wire hardness testing method: Divide the cross-section of the steel wire into two equal parts by radius, and test the hardness at three points from the surface to the core. Then analyze the hardness difference across the cross-section. See the schematic diagram. Figure 2 .

[0075] The test results are shown in Table 9.

[0076] Table 9. Difference in cross-sectional hardness between wire rod (HV1) and steel wire (HV0.2)

[0077] Example Wire rod steel wire 1 14.9 2 2 8.9 4 3 32.1 8 4 12 2 5 28.3 2 6 15.8 3

[0078] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A type of wire rod for fine steel wire cord, characterized in that, The chemical composition of the wire rod, by mass percentage, includes: C: 0.79%~0.84%, Si: 0.15%~0.30%, Mn: 0.45%~0.55%, P≤0.015%, S: 0.0030%~0.010%, total oxygen: 0.0008%~0.0022%, Als: 0.0002%~0.0012%, Mg: 0.0002%~0.0012%, Nb: 0.0003%~0.0009%, Mo: 0.0003%~0.0012%, balance being Fe and unavoidable impurities; The method for manufacturing the wire rod includes the following steps: (1) Continuous casting: The molten steel is continuously cast. The cross-sectional dimensions of the continuously cast billet are (250~300) mm × (350~400) mm. The grain size on the surface of the continuously cast billet is 260~520 μm, and the grain size in the core of the continuously cast billet is 800~1100 μm. The carbon segregation index at the 1 / 2 thickness position on the center line of the cross-sectional length of the continuously cast billet is controlled at 0.95~1.07, the carbon segregation index at the 1 / 4 thickness position on the center line of the cross-sectional length of the continuously cast billet is controlled at 0.96~1.06, and the carbon segregation index at the surface position on the center line of the cross-sectional length of the continuously cast billet is controlled at 0.94~1.

0. (2) Heating and rolling: The continuous casting billet is hot-charged, and the total time in the furnace is 3.8~4.5h. The temperature of the soaking zone is 1230~1280℃, and the holding time of the soaking zone is 40~60min. After heating, the continuous casting billet is continuously rolled into a square billet. The final rolling temperature of the continuous rolling is 940~1050℃, and the cross-sectional size of the square billet is (140~180)mm×(140~180)mm. (3) Wire rod rolling: The total time of the billet in the furnace is 150~170min, the temperature of the soaking zone is 1130~1170℃, the holding time of the soaking zone is 30~50min, after the billet is heated, it is rolled into wire rod after rough rolling, intermediate rolling, pre-finish rolling, finish rolling and double module rolling. The wire rod rolling specification is 5.0~6.0mm; (4) Wire rod cooling: After spinning, the wire rod is cooled on the air-cooled roller conveyor. The temperature at which cementite begins to precipitate in the wire rod is controlled at 740~770℃, and the supercooling degree of pearlite phase transformation in the wire rod is controlled at 100~150℃. When the phase transformation time on the air-cooled line is 4~6s, the pearlite content in the wire rod is ≥50%; when the phase transformation time is 14~16s, the pearlite content is ≥95%.

2. The fine steel wire cord strip according to claim 1, characterized in that, The ferrite Si content in the pearlitic structure of the wire rod is 0.15%~0.45%.

3. A method for manufacturing a fine steel wire cord coil as described in any one of claims 1-2, the method comprising the following steps: (1) Continuous casting: The molten steel is continuously cast. The cross-sectional dimensions of the continuously cast billet are (250~300) mm × (350~400) mm. The grain size on the surface of the continuously cast billet is 260~520 μm, and the grain size in the core of the continuously cast billet is 800~1100 μm. The carbon segregation index at the 1 / 2 thickness position on the center line of the cross-sectional length of the continuously cast billet is controlled at 0.95~1.07, the carbon segregation index at the 1 / 4 thickness position on the center line of the cross-sectional length of the continuously cast billet is controlled at 0.96~1.06, and the carbon segregation index at the surface position on the center line of the cross-sectional length of the continuously cast billet is controlled at 0.94~1.

0. (2) Heating and rolling: The continuous casting billet is hot-charged, and the total time in the furnace is 3.8~4.5h. The temperature of the soaking zone is 1230~1280℃, and the holding time of the soaking zone is 40~60min. After heating, the continuous casting billet is continuously rolled into a square billet. The final rolling temperature of the continuous rolling is 940~1050℃, and the cross-sectional size of the square billet is (140~180)mm×(140~180)mm. (3) Wire rod rolling: The total time of the billet in the furnace is 150~170min, the temperature of the soaking zone is 1130~1170℃, the holding time of the soaking zone is 30~50min, after the billet is heated, it is rolled into wire rod after rough rolling, intermediate rolling, pre-finish rolling, finish rolling and double module rolling. The wire rod rolling specification is 5.0~6.0mm; (4) Wire rod cooling: After spinning, the wire rod is cooled on the air-cooled roller conveyor. The temperature at which cementite begins to precipitate in the wire rod is controlled at 740~770℃, and the supercooling degree of pearlite phase transformation in the wire rod is controlled at 100~150℃. When the phase transformation time on the air-cooled line is 4~6s, the pearlite content in the wire rod is ≥50%; when the phase transformation time is 14~16s, the pearlite content is ≥95%.

4. The method for manufacturing wire rod according to claim 3, characterized in that, In step (1), the molten steel consists of molten iron and scrap steel, with scrap steel accounting for 5% to 10% of the mass of the molten steel.

5. The method for manufacturing wire rod according to claim 3, characterized in that, Before the continuous casting process in step (1), the molten steel is smelted. The smelting process is as follows: after the molten steel is smelted in the converter, it is refined in the LF furnace. The LF furnace refining time is 30~50min, the refining temperature is 1450~1550℃, and argon gas is used for stirring during the molten steel refining process. The argon gas flow rate is 200~500NL / min.

6. The method for manufacturing wire rod according to claim 3, characterized in that, In step (3), the pre-finishing rolling temperature of the workpiece is 950~1000℃, and the temperature compensation deformation rate factor for the last pass of the pre-finishing rolling is (1.1~2.6) ×10. 13 s -1 The temperature of the workpiece entering the finishing mill is 880~960℃, and the temperature compensation deformation rate factor for the last pass of finishing milling is (1.6~3.2)×10. 14 s -1 The temperature of the double-module rolling mill is 890~940℃, and the temperature compensation deformation rate factor for the last pass of the double-module rolling mill is (4.5~9.9)×10. 14 s -1 .

7. The method for manufacturing wire rod according to claim 3, characterized in that, In step (3), the wire rod spinning temperature is 910~940℃.

8. A fine steel wire, characterized in that, The fine steel wire is manufactured from the wire rod as described in any one of claims 1-2.

9. A method for manufacturing the fine steel wire according to claim 8, characterized in that, The method for manufacturing the fine steel wire includes the following steps: a. Mechanical descaling: The wire rod undergoes mechanical descaling treatment, and the residual iron oxide scale on the wire rod surface is ≤0.07%; b. Wire rod drawing: Wire rod is drawn in multiple passes to produce intermediate wires with a diameter of 0.8~1.2mm; c. Heat treatment of intermediate wire: After heating the intermediate wire to 880~915℃, it undergoes a phase change at 555~575℃ after cooling; d. Wire drawing: The heat-treated intermediate wire is drawn into a steel wire with a diameter of 0.15~0.20mm.

10. A fine cord, characterized in that, The fine cord is made of the fine steel wire described in claim 8.

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