Grain-oriented steel wire and manufacturing method thereof

Abstract

The present invention relates to a grain-oriented steel wire and a manufacturing method thereof. More specifically, the present invention relates to: a grain-oriented steel wire comprising, in wt%, 0.10% or less of C, 0.005-0.050% of P, 0.80-2.00% of Si, 0.010-0.035% of Al, 0.05-0.20% of Mn, 0.010% or less of N, and 0.010% or less of S, with the remainder comprising Fe and inevitable impurities, wherein the orientation of the steel wire in the longitudinal direction satisfies the texture according to the following Expression 1; and a manufacturing method thereof. (Expression 1): {001} > {011}

Description

Directional steel wire and its manufacturing method

[0001] The present invention relates to a directional steel wire having excellent electromagnetic properties and a method for manufacturing the same.

[0002] Recently, many researchers have been developing axial flux motor technology to improve the fuel efficiency of electric vehicles. Unlike radial flux motors currently being commercialized in electric vehicles, axial flux motors are difficult to machine from electrical steel plates. Therefore, powder-sintered materials are used in these motors and are used in bicycles. However, powder-sintered materials have poor durability and electromagnetic properties, limiting motor efficiency.

[0003] To improve these problems, there is a prior art for an axial motor core using wire rod. The technology manufactures a motor core by drawing pure iron wire rod to manufacture steel wire, and to improve motor performance, the diameter is reduced to reduce iron loss, and to increase the steel wire filling ratio of the motor core, the wire is drawn into a regular hexagonal wire rod, and a regular hexagonal steel wire of 1.24 to 0.71 mm is used, and the core is manufactured after heat treatment in a reducing atmosphere.

[0004] On the other hand, in the case of these pure iron wires, there is a problem that they are suitable for low-rotation, high-torque motors, but are not suitable as materials for axial motors used in high-speed rotation, such as automobiles.

[0005] The purpose of the present invention to solve the above-described problem is to provide a directional steel wire having excellent iron loss and magnetic flux density, which can improve the efficiency of an axial motor for high-speed rotation by controlling the aggregate structure, and a method for manufacturing the same.

[0006] The technical problems to be achieved in this document are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0007] In order to achieve the above object, a directional steel wire according to one embodiment of the present invention includes, in wt%, C: 0.10% or less, P: 0.005% to 0.050%, Si: 0.80% to 2.00%, Al: 0.010% to 0.035%, Mn: 0.05% to 0.20%, N: 0.010% or less, S: 0.010% or less, the remainder being Fe and other unavoidable impurities, and the longitudinal direction of the steel wire can satisfy the aggregate structure of the following Equation 1.

[0008] (Formula 1): {001} > {011}

[0009] Additionally, the steel wire according to one embodiment of the present invention may further include 0.01% to 0.20% of the sum of Sn and Sb.

[0010] Additionally, the diameter of the steel wire according to one embodiment of the present invention may be 0.9 mm or less.

[0011] In addition, a method for manufacturing a oriented steel wire according to one embodiment of the present invention includes the steps of: heating a billet containing, in wt%, C: 0.10% or less, P: 0.005% to 0.050%, Si: 0.80% to 2.00%, Al: 0.010% to 0.035%, Mn: 0.05% to 0.20%, N: 0.010% or less, S: 0.010% or less, the remainder Fe, and other unavoidable impurities, and then rolling and cooling the billet to manufacture a wire rod; drawing the wire rod; recrystallization-annealing the drawn steel wire; repeating drawing and recrystallization-annealing the recrystallization-annealed steel wire N times; performing a final weak drawing on the drawn and recrystallization-annealed steel wire; and a final texture annealing on the final weakly drawn steel wire.

[0012] Additionally, the above-described pre-rolling according to one embodiment of the present invention can be performed at a finishing rolling temperature of 930 to 980°C.

[0013] In addition, the freshness according to one embodiment of the present invention can be performed so that the freshness reduction rate is 20 to 60%.

[0014] Additionally, the recrystallization annealing according to one embodiment of the present invention can be performed at 800 to 950°C.

[0015] Additionally, the final yield according to one embodiment of the present invention can be achieved at 4 to 19%.

[0016] Additionally, the final assembly structure annealing according to one embodiment of the present invention can be performed at 600 to 800°C.

[0017] According to one embodiment of the present invention, by forming a {001} aggregate structure in the longitudinal direction of the steel wire, iron loss can be reduced during the manufacture of an axial motor, thereby improving motor efficiency.

[0018] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided to fully convey the spirit of the present invention to those skilled in the art. The present invention is not limited to the embodiments presented herein and may be embodied in other forms. To clarify the present invention, the drawings may omit portions irrelevant to the description, and the sizes of components may be slightly exaggerated to facilitate understanding.

[0020] Additionally, when a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0021] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0022] The directional steel wire according to one embodiment of the present invention may include, in wt%, C: 0.10% or less, P: 0.005% to 0.050%, Si: 0.80% to 2.00%, Al: 0.010% to 0.035%, Mn: 0.05% to 0.20%, N: 0.010% or less, S: 0.010% or less, the remainder being Fe and other unavoidable impurities.

[0023] Below, the reasons for limiting the composition of the above steel wire are explained in detail. Unless otherwise specified, the composition below refers to weight %.

[0024] The carbon (C) content may be less than 0.10%.

[0025] C is an element that contributes to refining grains and improving drawability by causing phase transformation between ferrite and austenite, making it an essential element for improving the rollability of high-Si steel, which is brittle and has poor rollability. However, if it remains in the final manufactured wire rod, it is an element that worsens the magnetic properties by causing carbides formed due to the magnetic aging effect to precipitate in the steel sheet. If the C content in the billet is excessively high, the texture formed during texture annealing is deteriorated by carbides, which reduces magnetism. Furthermore, there is a problem that residual carbon in the final product deteriorates the magnetic properties due to magnetic aging. Considering this, the C content is preferably controlled to 0.10% or less, more preferably controlled to 0.08% or less, and most preferably controlled to 0.05% or less.

[0026] The phosphorus (P) content may be 0.005% to 0.050%.

[0027] P can play an auxiliary role by segregating at grain boundaries, thereby hindering the movement of grain boundaries and simultaneously suppressing grain growth, and has the effect of facilitating the formation of {001} / LD texture in terms of microstructure by suppressing non-uniform grain growth. If the P content is excessively high, there is a problem that the rollability and drawability are inferior because grain boundary embrittlement increases. On the other hand, if the P content is excessively low, there is a problem that the effect of hindering the movement of grain boundaries due to the addition of P and simultaneously suppressing grain growth is not expressed. Considering this, it is preferable to control the P content to 0.005 to 0.050%.

[0028] The silicon (Si) content can be 0.80% to 2.00%.

[0029] Silicon (Si) plays a very important role in increasing the resistivity of steel and reducing core loss. If the Si content is excessively high, an irregular decarburized layer may be formed on the surface, making it difficult to control the grain structure during the final annealing process. On the other hand, if the Si content is excessively low, the drag effect, which suppresses grain boundary growth during annealing, is reduced, making it difficult to control the grain structure during annealing. In particular, the eddy current loss may increase and the core loss characteristics may deteriorate due to the reduced resistivity reduction effect. Considering this, the Si content is preferably controlled to 0.80% to 2.00%, and more preferably, it is controlled to 1.00% to 1.80%.

[0030] The content of aluminum (Al) can be 0.010% to 0.035%.

[0031] Al acts as a strong grain growth inhibitor by combining with Si, Mn, or N to form nitrides in the form of (Al, Si, Mn)N and AlN. If the content of Al is excessively high, the remelting temperature of the Al-based nitrides becomes excessively high, so that they are not completely dissolved when the slab is reheated, resulting in precipitation with very uneven size and distribution even after the slab is reheated. In addition, the recrystallization behavior becomes unstable during recrystallization annealing, so that the magnetic properties of the final product deteriorate and the deviation increases. If the content of Al is excessively low, there is a problem that the role of the grain growth inhibitor cannot be fully expected. Considering this, it is preferable to control the content of Al to 0.010 to 0.035%.

[0032] The manganese (Mn) content can be 0.05% to 0.20%.

[0033] Mn, like Si, not only has the effect of improving iron loss by increasing the resistivity of electrical steel sheets and reducing eddy current loss, but also reacts with S in the annealed state to form Mn-based sulfides, thereby suppressing the formation of grain boundary sulfides and thus suppressing continuous casting cracks. In addition, by forming (Al, Si, Mn)N precipitates, it can suppress grain growth during recrystallization annealing and facilitate the formation of texture during the final texture annealing. If the content of Mn is excessively high, since Mn is an austenite stabilizing element, the austenite phase fraction increases during the final recrystallization annealing, which hinders the formation of {001} / LD texture and may decrease the magnetic flux density. If the content of Mn is excessively low, the aforementioned effect is not achieved, and there is a problem of reduced drawability due to surface cracks in the final product. Considering this, it is preferable to control the content of Mn to 0.05% to 0.20%.

[0034] The nitrogen (N) content may be less than 0.010%.

[0035] Nitrogen reacts with aluminum (Al) to form aluminum nitride (AlN), which is utilized to control grain size. Excessive nitrogen content can coarsen aluminum nitride, reducing grain growth efficiency. Therefore, it is recommended to control the nitrogen content to 0.010% or less.

[0036] The sulfur (S) content may be less than 0.010%.

[0037] S inhibits grain growth by forming manganese sulfide (MnS) precipitates within the billet. If the content of S is excessively high, it segregates in the center during continuous casting, and the manganese sulfide precipitates are not uniformly precipitated during the subsequent wire rolling process, which causes a problem of non-uniform microstructure. In addition, since the formation of manganese sulfide occurs unstable, there is a problem that it is difficult to control sulfide by Sn or Sb. Considering this, it is preferable to control the content of S to 0.010% or less.

[0038] The combined content of tin (Sn) and antimony (Sb) can be from 0.01% to 0.20%.

[0039] Sn or Sb, like P, has the effect of segregating at grain boundaries and inhibiting the growth and movement of grains. This has the effect of stabilizing secondary recrystallization by supplementing the insufficient grain growth inhibition for secondary recrystallization behavior during high-temperature annealing. To achieve this grain growth inhibition effect, Sn or Sb can be used alone or in combination. If the content of Sn or Sb is excessively large, the grain growth inhibition effect becomes excessively large, making it difficult to obtain a stable recrystallized texture, and there is a problem that the surface quality deteriorates due to surface grain boundary oxidation. On the other hand, if the content of Sn or Sb is excessively low, there is a problem that the aforementioned effect is insufficient. Considering this, it is preferable to control the sum of Sn and Sb to 0.01% to 0.20%.

[0040] The remaining component of the present invention is iron (Fe). However, during the typical manufacturing process, unintended impurities from raw materials or the surrounding environment may inevitably be mixed in, and thus cannot be excluded. Since these impurities are readily apparent to anyone skilled in the art of typical manufacturing, their full details are not specifically discussed in this specification.

[0041] In one embodiment of the present invention, a directional steel wire can have a longitudinal direction of the steel wire that satisfies the aggregate structure of Equation (1).

[0042] Equation (1): {001} > {011}

[0043] The texture of the steel wire can be confirmed by measuring EBSD by cutting the wire in the cross-section C section or by observing XRD to obtain an inverse pole figure (IPF) map. Since the magnetic field flows in the longitudinal direction of the steel wire during the manufacture of the motor core, if the texture of the {001} plane, which is the shortest axis of the cubic in the longitudinal direction of the steel wire, is formed, the iron loss is reduced. Normally, carbon steel, which is BCC, has a problem in that the {011} deformation texture is formed during drawing, which increases the iron loss and lowers the motor efficiency.

[0044] In addition, the directional steel wire according to one embodiment of the present invention can satisfy a diameter of 0.90 mm or less after fresh processing. As shown in Equation (2) below, since the eddy current loss (Pv) is proportional to the square of the wire diameter, a reduction in the diameter is necessary.

[0045] Equation (2): Pν∝(fΒ m d) 2 / ρ

[0046] (Here, Pν: eddy current loss, f: frequency, β m : magnetic flux density amplitude, d: diameter of magnetic material, ρ: electrical resistivity of magnetic material)

[0047] Therefore, it is desirable to ensure appropriate fresh processability and ensure that the diameter of the steel wire is 0.90 mm or less.

[0048] Next, a method for manufacturing a directional steel wire according to one embodiment of the present invention will be described.

[0049] A method for manufacturing a oriented steel wire according to one embodiment of the present invention comprises the steps of: heating a billet containing, in wt%, C: 0.10% or less, P: 0.005% to 0.050%, Si: 0.80% to 2.00%, Al: 0.010% to 0.035%, Mn: 0.05% to 0.20%, N: 0.010% or less, S: 0.010% or less, the remainder Fe, and other unavoidable impurities, and then performing wire rolling and cooling to manufacture a wire rod; drawing the wire rod; recrystallization annealing the drawn steel wire; repeating drawing and recrystallization annealing N times for the recrystallization annealed steel wire; and finally lightly drawing the drawn and recrystallization annealed steel wire.

[0050] The reason for limiting the composition range of each alloy element is as described above, and each manufacturing step is explained in more detail below.

[0051] First, a billet having the above-described composition is heated.

[0052] Afterwards, when the heating of the billet is completed, wire rolling is performed to manufacture wire. The wire can be rolled at a finish rolling temperature of 930℃ to 980℃, and preferably, it is rolled at 930℃ to 960℃. If the finish rolling temperature is lower than 930℃, decarburization due to phase transformation in the surface layer is accelerated, which may result in a non-homogeneous carbon content in the surface layer, which may form coarse grains, or phase transformation may occur below the Ar3 temperature due to a locally supercooled area, which may form fine grains, making it difficult to form the desired texture during drawing and annealing. If it exceeds 980℃, the rolling temperature is high, which causes the grain size to become coarse and non-homogeneous, making it difficult to form the desired texture during drawing and annealing.

[0053] Next, the step of annealing the above-mentioned wire at least once may be included.

[0054] At this time, the freshness can be divided and performed N times so that the maximum freshness reduction rate is 20 to 60%, preferably 30 to 60%. If the maximum freshness reduction rate is less than 20%, the freshness reduction rate is low, so that uniform stress is not applied to each grain, and thus abnormal grain growth may occur during recrystallization annealing. If it exceeds 60%, the strain {011} texture develops, and it may not be controlled into a texture close to random during recrystallization annealing.

[0055] The recrystallization annealing step of the above-described fresh steel wire can be performed at 800°C to 950°C, preferably 850°C to 950°C. If the recrystallization annealing temperature is lower than 800°C, the deformed {011} texture may not be sufficiently resolved, and if the recrystallization annealing temperature exceeds 950°C, the grain size may become coarser, which may lower the workability during subsequent drawing and make it difficult to control the texture.

[0056] The above fresh and recrystallization annealing can be repeated at least once.

[0057] The above fresh and recrystallized annealed steel wire can be subjected to final drawing and final texture annealing.

[0058] The final drawing can be performed at 4 to 19%, preferably 5 to 15%. In the case of drawing with a small amount of processing, the processing is applied only to the surface grains, and the processing effect is small toward the center. Through this, the texture close to {001} / LD on the surface formed during the previous recrystallization grows toward the center through Ostwald ripening during texture annealing, forming a {001} texture. During drawing, the surface is in indirect tension mode, and the grains close to {001} are subjected to the most shear deformation, so the stored energy is high, and these unstable grains with high stored energy grow during the subsequent texture annealing. When the annealing ratio is less than 4%, the surface grain size has little processing effect, making it difficult to grow {001} grain texture through Oswalt growth. When it exceeds 19%, the processing amount is high, forming {011} deformation texture, making it difficult to control {001} texture during texture annealing.

[0059] The final texture annealing described above is an annealing that grows unstable surface grains after weak drawing, and can be performed at 600°C to 800°C, preferably 600°C to 750°C. If the final texture annealing is less than 600°C, the energy accumulated in the surface grains during weak drawing may not have enough driving force to cause growth, and if it exceeds 800°C, recrystallization may be induced, causing the texture to change randomly.

[0060] Hereinafter, the present invention will be described in more detail through examples. However, the description of these examples is intended only to illustrate the implementation of the present invention and is not intended to limit the present invention. This is because the scope of the present invention is determined by the matters set forth in the patent claims and matters reasonably inferred therefrom.

[0061] Example

[0062] Ingots having the alloy composition shown in Table 1 below were rolled to a diameter of Φ5.5 mm at a finishing wire rolling temperature of 940°C, and after pickling and coating, drawing and annealing were performed to produce a steel wire with a final diameter of 0.7 mm. At this time, drawing was performed to 3.5 mm, 2.4 mm, 1.55 mm, 1.0 mm, and 0.75 mm, respectively, and the intermediate wire was annealed at 900°C after each drawing. After that, the 0.75 mm intermediate wire was slightly drawn to 0.7 mm, and the final texture annealing was performed at 650°C in a reducing atmosphere.

[0063] After cutting 20 steel wires with a final diameter of 0.7 mm into the C-section, the texture was observed using EBSD. The {001} Max. value in Table 1 below is the value that appears in the program when the IPF is drawn after removing error data with a Confidence Index of less than 0.1 using the TSL OIM program. The Max value at this time indicates that the texture was formed regardless of the {001}, {110}, and {111} directions. When researchers in general observed the IPF, they expressed it as {001} Max. only when the texture was developed in {001}. In addition, in the present invention, it was assumed that the texture was formed when the {001} texture was formed with a Max. value of 2 or more. Therefore, values ​​less than 2 in the {001} Max. value in Table 1 below were randomly indicated.

[0064] CPSiAlMnNSSn+Sb{001} MaxRemarksExperimental Example 10.10.0071.640.030.140.0040.0050.012.4Experimental Example 20.080.0090.810.0190.130.0030.0040.012.3Experimental Example 30.060.0051.480.0340.140.0040.0060.012.9Experimental Example 40.040.0211.690.0290.150.0040.0050.013.3Experimental Example 50.020.0131.350.0240.140.0040.0050.013.5Experimental Example 60.020.0091.9 70.0210.150.0050.0050.014.2Experimental Example70.020.0481.880.0330.150.0040.0040.24.8Experimental Example80.020.0271.740.0310.150.0040.0060.013.1Comparative Example10.130.011.750.0280.140.0040.0050.01RandomComparative Example20.040.0041.570.030.130.0040.0050.01RandomComparative Example30.040.0511.680.0220.140.0040 .0050.01-Rolled crack comparison example 40.050.0120.750.030.150.0050.0040.01Random comparison example 50.040.0112.030.0310.160.0040.0050.01-Fresh crack comparison example 60.040.0091.440.0070.140.0040.0050.01Random comparison example 70.040.011.650.040.150.0040.0040.01Random comparison example 80.050.0081.380.0220.0480.0040.0050.01 Rolling crack comparison example 90.040.0071.550.0270.210.0040.0050.01Random comparison example 100.040.0121.490.0310.150.0120.0050.01Random comparison example 110.040.0121.510.0320.140.0040.0110.01-Fresh crack comparison example 120.040.0141.770.030.150.0030.0050.008Random comparison example 130.040.0121.780.030.150.0040.0050.21-Rolling crack

[0065] As shown in Table 1 above, it can be confirmed that Experimental Examples 1 to 8, which satisfy the alloy composition and manufacturing process suggested in the present invention, have a {001} texture well formed in the longitudinal direction of the steel wire. On the other hand, in the case of Comparative Example 1, the C content was high, so the texture formation was worsened by the formed Fe carbide, and a random texture was formed. In the case of Comparative Example 2, the P content was low, so grain control was not possible during annealing, and a random texture was formed. In the case of Comparative Example 3, the P content was high, so cracks were formed during wire rolling. In addition, in the case of Comparative Example 4, the Si content was low, so grain growth control was not possible during annealing, and a random texture was formed. In the case of Comparative Example 5, the Si content was high, so cracks occurred during wire drawing. In Comparative Example 6, the Al content was low, so grain growth control was not achieved during annealing, resulting in the formation of a random texture. In Comparative Example 7, the Al content was high, so the size and distribution of AlN, which controls grain growth, were precipitated very non-uniformly, resulting in unstable recrystallization behavior during annealing, confirming that a random texture was formed. In Comparative Example 8, the Mn content was low, so cracks occurred during wire rolling due to iron-based sulfides formed during continuous casting. In Comparative Example 9, the Mn content was high, so homogeneous grain control was not achieved during wire rolling and annealing, confirming that a random texture was formed. In Comparative Example 10, the N content was high, so the AlN, which controls grain growth, were precipitated very non-uniformly, resulting in unstable recrystallization behavior during annealing, confirming that a random texture was formed. In Comparative Example 11, the S content was high, so cracks occurred during wire drawing. Comparative Example 12 had a low Sn or Sb content, so grain growth control was not possible during annealing, resulting in the formation of a random aggregate structure. Comparative Example 13 had a high Sn or Sb content, so cracks were formed during wire rolling.

[0066] Using a wire having the chemical composition of Experimental Example 6 of Table 1 above, a steel wire was manufactured by varying the wire rolling temperature, maximum draw reduction ratio, annealing temperature, weak draw reduction ratio, final texture annealing temperature, etc. as shown in Table 2 below, and the {001} Max. value was shown.

[0067] Wire rolling temperature (℃)Maximum drawing reduction rate (%)Annealing temperature (℃)Weak drawing reduction rate (%)Final texture Annealing temperature (℃){001} MaxExperimental example694059.590012.96504.2Comparative example1492559.590012.9650RandomComparative example1598759.590012.9650RandomComparative example169401990012.9650RandomComparative example179406390012.9650RandomComparative example1894059.57971 2.9650RandomComparison Example 1994059.595112.9650RandomComparison Example 2094059.59003.9650RandomComparison Example 2194059.590019.2650RandomComparison Example 2294059.590012.9598RandomComparison Example 2394059.590012.9801Random

[0068] As shown in Table 2 above, it can be confirmed that Experimental Example 6, which satisfies the alloy composition and manufacturing process conditions presented in the present invention, has a {001} texture well formed in the longitudinal direction of the steel wire. On the other hand, Comparative Example 14 had a low wire rolling temperature, so the texture control was not possible due to non-homogeneous grains formed by transformation during rolling locally below the Ar3 temperature. Comparative Example 15 had a high wire rolling temperature, so the grain size became coarse and non-homogeneous, and the texture control was not possible.

[0069] In addition, Comparative Example 16 had a low maximum reduction in area, so that uniform stress was not applied during drawing, and thus texture control was not achieved due to abnormal grain growth. Comparative Example 17 had a high maximum reduction in area, so that the {110} deformation texture formed during drawing was greatly developed, and texture control was not achieved.

[0070] In Comparative Example 18, the annealing temperature was low, so the {110} deformation structure was not resolved, and thus the texture control was not achieved. In Comparative Example 19, the annealing temperature was high, so the grain size was coarse and uncontrollable, and thus the texture control of the steel wire was not achieved.

[0071] In Comparative Example 20, the weak reduction rate was low, so the surface crystal grains had low stored energy and did not grow during the final texture annealing, and thus texture control was not possible. In Comparative Example 21, the weak reduction rate was high, so the surface crystal grains formed a {110} deformation texture, and texture control was not possible.

[0072] In addition, in Comparative Example 22, the final texture annealing temperature was low, so the energy accumulated in the surface grains did not have enough driving force to grow the grains, and thus texture control was not achieved. In Comparative Example 23, the final texture annealing temperature was high, so recrystallization of the surface grains occurred, and texture control was not achieved.

[0073] Although the embodiments of the invention disclosed above have been illustrated and described, the disclosed invention is not limited to the specific embodiments described above, and various modifications may be implemented by a person having ordinary skill in the art to which the disclosed invention pertains without departing from the gist claimed in the claims.

Claims

1. Contains, in wt%, C: 0.10% or less, P: 0.005% to 0.050%, Si: 0.80% to 2.00%, Al: 0.010% to 0.035%, Mn: 0.05% to 0.20%, N: 0.010% or less, S: 0.010% or less, the remainder being Fe and other unavoidable impurities. Directional steel wire whose longitudinal direction satisfies the set structure of Equation 1 below. (Formula 1): {001} > {011} 2. In paragraph 1, The above steel wire further contains 0.01% to 0.20% of the sum of Sn and Sb.

3. In paragraph 1, Steel wire having a diameter of 0.9mm or less.

4. A step of manufacturing a wire rod by heating a billet containing, by weight%, C: 0.10% or less, P: 0.005% to 0.050%, Si: 0.80% to 2.00%, Al: 0.010% to 0.035%, Mn: 0.05% to 0.20%, N: 0.010% or less, S: 0.010% or less, the remainder being Fe and other unavoidable impurities, and then performing wire rolling and cooling; The step of refreshing the above-mentioned pre-processing material; A step of recrystallizing the fresh steel wire; A step of repeating the drawing and recrystallization annealing of the above recrystallized steel wire N times; The step of final drawing of the above fresh and recrystallized steel wire; and A step of annealing the above final annealed steel wire to a final assembly structure; A method for manufacturing a directional steel wire comprising:

5. In paragraph 4, The above-mentioned wire rolling is a method for manufacturing steel wire, which is performed at a finishing rolling temperature of 930 to 980°C.

6. In paragraph 4, The above freshness is a method for manufacturing steel wire in which the maximum freshness reduction rate is 20 to 60%.

7. In paragraph 4, The above recrystallization annealing is a method for manufacturing steel wire, performed at 800 to 950°C.

8. In paragraph 4, A method for manufacturing a steel wire in which the final strength is 4 to 19%.

9. In paragraph 4, The above final annealing process for manufacturing steel wire is performed at 600 to 800°C.