Soft magnetic steel wire rod, steel wire, and method for manufacturing soft magnetic steel wire

Abstract

A soft magnetic steel wire rod is provided, which comprises, in weight%, 0.0001 to 0.0300% of C, 0.001 to 3.000% of Si, 0.001 to 0.500% of Mn, 0.001 to 0.100% of Al, 0.0001 to 0.0100% of P, 0.0001 to 0.0100% of S, 0.0001 to 0.0100% of N, and the remainder being Fe and other inevitable impurities, wherein, after the soft magnetic steel wire rod is drawn at room temperature at a reduction ratio of 59% to 93%, the number density of shear bands of the steel wire is 11.4 / mm2 or more.

Description

Method for manufacturing soft magnetic wire, steel wire, and soft magnetic steel wire

[0001] The present invention relates to a soft magnetic wire, a steel wire, and a method for manufacturing a soft magnetic steel wire having excellent electromagnetic properties. In particular, it relates to a steel material suitable for manufacturing iron cores for motors, generators, solenoid valves, relays, etc., used in various electrical components such as automobiles, railways, and home appliances, and a method for manufacturing the same.

[0002] With the recent tightening of regulations regarding environmental preservation and energy conservation, there is a growing demand for improved efficiency in motors and generators. To enhance the efficiency of motors and generators, it is crucial to improve the electromagnetic properties of the steel materials used. In particular, high permeability, high magnetic flux density, and low iron loss are required. Furthermore, depending on the application and shape of the component, a certain level of strength and hot and cold forgeability may also be necessary. For these reasons, low-carbon steel is typically used for motors and generators because it offers magnetic flux density that responds easily to external magnetic fields while satisfying requirements for strength and forgeability.

[0003] Until now, the stator cores of radial motors, which are used as drive motors for electric vehicles, have been manufactured by punching electrical steel sheets into a single uniform shape and then stacking dozens to hundreds of sheets. However, due to the structure of axial flux motor stator cores, electrical steel sheets cannot be punched into a single shape; instead, sheets ranging from dozens to as many as the number of sheets to be stacked must be punched, and the punched sheets of different shapes must be stacked in an axially symmetric manner. Consequently, compared to radial motor cores, the manufacturing process is very complex and lengthy, requiring relatively high costs. Against this backdrop, a method of manufacturing axial flux motor stator cores by forming soft magnetic metal powder is sometimes preferred over punching electrical steel sheets. This is because using powder materials allows for significant cost savings by greatly simplifying the manufacturing process, even if the electromagnetic properties are slightly inferior.

[0004] However, considering that improving the efficiency of the drive motor is the top priority for enhancing the energy efficiency of electric vehicles, and that drive motors for Urban Air Mobility (UAM), which has recently been receiving attention, require high output, there was a problem in that it was difficult to ignore the electromagnetic properties of materials for the stator core.

[0005] In order to solve the aforementioned problems, one embodiment of the present invention aims to provide a soft magnetic wire, a steel wire, and a method for manufacturing a soft magnetic steel wire, which are easier to manufacture than steel plates and have superior electromagnetic properties than powders, as materials for the stator core of an axial magnetic flux motor.

[0006] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description below.

[0007] According to one embodiment of the present invention as a means to achieve the above-mentioned purpose, the soft magnetic wire may comprise, in weight percent, C: 0.0001 to 0.0300%, Si: 0.001 to 3.000%, Mn: 0.001 to 0.500%, Al: 0.001 to 0.100%, P: 0.0001 to 0.0100%, S: 0.0001 to 0.0100%, N: 0.0001 to 0.0100%, and the remainder being Fe and other unavoidable impurities. After drawing at room temperature with a reduction rate of 59 to 93%, the number density of shear bands of the steel wire may be 11.4 bands / mm² or more.

[0008] According to one embodiment of the present invention, the soft magnetic steel wire may comprise, in weight percent, C: 0.0001 to 0.0300%, Si: 0.001 to 3.000%, Mn: 0.001 to 0.500%, Al: 0.001 to 0.100%, P: 0.0001 to 0.0100%, S: 0.0001 to 0.0100%, N: 0.0001 to 0.0100%, and the remainder being Fe and other unavoidable impurities. The average grain size of the ferrite of the soft magnetic steel wire may be 260 μm or more. The magnetic flux density of the soft magnetic steel wire may be 1.76 T or more.

[0009] According to one embodiment of the present invention, a method for manufacturing a soft magnetic steel wire may include the steps of preparing a wire rod, drawing, and annealing heat treatment.

[0010] The step of preparing the above wire rod may include, in weight percent, preparing a wire rod comprising C: 0.0001 to 0.0300%, Si: 0.001 to 3.000%, Mn: 0.001 to 0.500%, Al: 0.001 to 0.100%, P: 0.0001 to 0.0100%, S: 0.0001 to 0.0100%, N: 0.0001 to 0.0100%, and the remainder being Fe and other unavoidable impurities.

[0011] The above drawing step may include a step of drawing the wire at room temperature with a reduction rate of 59 to 93% so that the number density of the shear bands is 11.4 pieces / mm² or more.

[0012] The above annealing heat treatment step may include an annealing step in which the drawn wire is heated to a range of (A1 - 110)℃ to (A1 + 200)℃ and maintained for at least 10 minutes.

[0013] According to an embodiment of the present invention, the invention aims to provide a soft magnetic wire, a steel wire, and a method for manufacturing a soft magnetic steel wire that is easier to manufacture than electrical steel sheets and has superior electromagnetic properties compared to powders.

[0014] FIG. 1 is a flowchart illustrating a method for manufacturing a soft magnetic steel wire according to one embodiment of the present invention.

[0015] Figure 2 is a photograph showing the shear band of the steel wire after the drawing step of Comparative Example 3 among the experimental examples of the present invention.

[0016] Figure 3 is a photograph showing the shear band of the steel wire after the drawing step of Example 2 among the experimental examples of the present invention.

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. In this specification, the same reference numerals denote the same elements throughout. Furthermore, various elements and areas in the drawings are depicted schematically. Accordingly, the technical concept of the present invention is not limited by the relative sizes or spacing depicted in the attached drawings. The terms used in this specification are intended to describe the present invention and are not intended to limit the present invention. Additionally, singular forms used in this specification include plural forms unless the relevant definitions clearly indicate otherwise.

[0018] Unless otherwise noted, units are weight percent. Furthermore, when a part is described as "containing" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0019] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms defined in advance are interpreted to have meanings consistent with relevant technical literature and the presently disclosed content.

[0020] Additionally, terms such as "about," "substantially," etc., in this specification are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the said sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosed content in which precise or absolute values ​​are mentioned to aid in understanding the invention.

[0021] Soft magnetic wire

[0022] [furtherance]

[0023] A soft magnetic wire according to one embodiment of the present invention may comprise, in weight percent, C: 0.0001 to 0.0300%, Si: 0.001 to 3.000%, Mn: 0.001 to 0.500%, Al: 0.001 to 0.100%, P: 0.0001 to 0.0100%, S: 0.0001 to 0.0100%, N: 0.0001 to 0.0100%, and the remainder being Fe and other unavoidable impurities. Hereinafter, the composition and the reasons for setting the compositional content of the soft magnetic wire according to one embodiment of the present invention will be explained.

[0024] Carbon (C): 0.0001 to 0.0300%

[0025] Carbon is the most important element determining strength and ductility in steel; as the content increases, strength increases and ductility decreases. For efficient steel production, a lower limit of carbon content of 0.0001% is preferable, as manufacturing costs increase significantly if the content is lowered. The electromagnetic properties of steel improve as the ferromagnetic ferrite fraction within the microstructure increases. If the carbon content becomes excessive, not only does the ferrite fraction decrease, but the electromagnetic properties deteriorate because cementite, which hinders domain wall movement, precipitates. Therefore, the upper limit of carbon content is preferably 0.0300%. More preferably, it is 0.0280%.

[0026] Si (Silicon): 0.001 to 3.000%

[0027] Although Si acts as a deoxidizer, it is the most important element for improving iron loss by lowering the magnetic anisotropy of steel and increasing resistivity. If the Si content is less than 0.001%, the effect of improving iron loss becomes negligible. Conversely, if it exceeds 3.000%, brittleness increases and processing becomes difficult. Therefore, the upper limit of the Si content is preferably 3.000%. More preferably, it is 2.741%.

[0028] Mn (Manganese): 0.001 to 0.500%

[0029] Mn not only acts as an efficient deoxidizer but also contributes to improved machinability by combining with S within the steel to disperse and precipitate MnS, thereby increasing the segmentality of cutting chips generated during machining. To exhibit this effect, the Mn content must be 0.001% or higher. On the other hand, if the Mn content is too high, MnS is formed excessively, which actually deteriorates electromagnetic properties; therefore, it is desirable to contain 0.500% or less. Accordingly, the upper limit of the Mn content is preferably 0.500%. More preferably, it is 0.437%.

[0030] Al (Aluminum): 0.001 to 0.100%

[0031] Since Al is a powerful deoxidizer, it is desirable to have a content of at least 0.001%. However, because Al combines with N within the steel to form AlN, which acts as pinning grains that inhibit grain growth during heat treatment after drawing, thereby increasing grain boundaries that hinder domain wall movement and deteriorating electromagnetic properties, the upper limit of the Al content is preferably 0.100% or less. More preferably, it is 0.092%.

[0032] P (Phosphorus): 0.0001 to 0.0100%

[0033] P is an impurity element that causes grain boundary segregation within steel, thereby degrading electromagnetic properties. Therefore, it is desirable for the P content to be 0.0100% or less. More preferably, it is 0.009%. However, generally, it is contained at 0.0001% or more, and since additional processes requiring significant costs are required to reduce it to below that level, a lower limit of 0.0001% is desirable.

[0034] S (Sulfur): 0.0001 to 0.0100%

[0035] Since S is not only an impurity element but also forms MnS which is harmful to electromagnetic properties, the S content is preferably 0.0100% or less. More preferably, it is 0.008% or less. However, generally, it is contained at 0.0001% or more, and since additional processes at significant cost are required to reduce it to below that level, the lower limit is preferably 0.0001%.

[0036] N (Nitrogen): 0.0001 to 0.0100%

[0037] As N is a nitride-forming element, when it combines with Al to form AlN, it acts as pinning grains that inhibit grain growth during heat treatment after drawing, thereby increasing grain boundaries that hinder domain wall movement and deteriorating electromagnetic properties. Therefore, it is desirable for the N content to be 0.0100% or less. More preferably, it is 0.008% or less. However, generally, it is contained at 0.0001% or more, and since reducing it to below that level requires additional processes at significant cost, the lower limit is preferably 0.0001%.

[0038] Other ingredients

[0039] The remaining component of the present invention is iron (Fe). However, since unintended impurities from raw materials or the surrounding environment may inevitably be incorporated during the ordinary manufacturing process, they cannot be excluded. As these impurities are known to any person skilled in the ordinary manufacturing process, all details thereof are not specifically mentioned in this specification.

[0040] According to one embodiment of the present invention, the soft magnetic wire may have a shear band number density of 11.4 bands / mm² or more after being drawn at room temperature with a reduction rate of 59 to 93%.

[0041] The above soft magnetic wire may have a shear band number density of 1.0 band / mm² or less after an annealing heat treatment in which it is heated to a range of (A1 - 110)℃ to (A1 + 200)℃ and maintained for 10 minutes or more.

[0042] The above soft magnetic wire may have an average ferrite grain size of 260㎛ or more after an annealing heat treatment in which the wire is heated to a range of (A1 - 110)℃ to (A1 + 200)℃ and maintained for 10 minutes or more.

[0043] The above soft magnetic wire may have an average ferrite grain size of 66㎛ to 200㎛ prior to drawing.

[0044] The above soft magnetic wire may have a magnetic flux density of 1.76T or higher after an annealing heat treatment in which it is heated to a range of (A1 - 110)℃ to (A1 + 200)℃ and maintained for 10 minutes or more.

[0045] The microstructure of the above soft magnetic wire may contain 99% or more of ferrite in terms of area fraction.

[0046] Soft magnetic steel wire

[0047] A soft magnetic steel wire according to one embodiment of the present invention may comprise, in weight%, C: 0.0001 to 0.0300%, Si: 0.001 to 3.000%, Mn: 0.001 to 0.500%, Al: 0.001 to 0.100%, P: 0.0001 to 0.0100%, S: 0.0001 to 0.0100%, N: 0.0001 to 0.0100%, and the remainder being Fe and other unavoidable impurities.

[0048] A soft magnetic steel wire according to one embodiment of the present invention may have an average ferrite grain size of 260 μm or more and a magnetic flux density of 1.76 T or more. The average ferrite grain size of the soft magnetic steel wire may be 260 μm or more. If the grain size of the steel wire is excessively small, the influence of grain boundaries hindering the movement of magnetic domain walls increases, leading to an increase in coercivity. Therefore, it is desirable to increase the grain size to reduce the density of grain boundaries.

[0049] The above soft magnetic steel wire may have a magnetic flux density of 1.76T or more.

[0050] The above soft magnetic steel wire may have a shear band number density of 1.0 band / mm² or less.

[0051] The microstructure of the above soft magnetic steel wire may contain 99% or more of ferrite as an area fraction.

[0052] Method for manufacturing soft magnetic steel wire

[0053] FIG. 1 is a flowchart illustrating a method for manufacturing a soft magnetic steel wire according to one embodiment of the present invention.

[0054] Referring to FIG. 1, a method for manufacturing a soft magnetic steel wire according to one embodiment of the present invention comprises the steps of: preparing a wire rod (S100); drawing the wire rod (S200); and heating the drawn wire rod and then performing annealing heat treatment (S300). Hereinafter, the method for manufacturing a soft magnetic steel wire according to the present invention will be described in detail step by step.

[0055] (S100) Preparing stage

[0056] According to one embodiment of the present invention, the method may include the step of preparing a wire rod comprising, in weight percent, C: 0.0001 to 0.0300%, Si: 0.001 to 3.000%, Mn: 0.001 to 0.500%, Al: 0.001 to 0.100%, P: 0.0001 to 0.0100%, S: 0.0001 to 0.0100%, N: 0.0001 to 0.0100%, and the remainder being Fe and other unavoidable impurities.

[0057] The reason for setting the composition and composition content of the above-mentioned wire material may be the same as that of the soft magnetic wire material according to one embodiment of the present invention described above.

[0058] According to one embodiment of the present invention, the method may include the step of preparing a wire rod containing 99% or more of ferrite in an area fraction as a microstructure. Since the magnetic properties of the soft magnetic wire rod are important, it is preferable that the microstructure of the wire rod be a single-phase ferrite (a) structure. A single-phase ferrite structure means containing 99% or more of ferrite in an area fraction, or 100% in area.

[0059] One embodiment of the present invention may include the step of providing a wire rod having an average grain size of ferrite in a microstructure of 66 μm or more. If the grain size of the wire rod is excessively small, the influence of grain boundaries hindering the movement of domain walls increases, leading to an increase in coercivity. Therefore, it is desirable to increase the grain size to reduce the density of grain boundaries. Accordingly, the average grain size of the ferrite microstructure of the wire rod may be 66 μm or more.

[0060] In one example, the wire rod may be manufactured by including the steps of: manufacturing a billet; heating the billet at 1000°C to 1200°C; rolling the heated billet; finishing rolling at A1°C to (A1 + 100)°C after the rolling step; and cooling after the finishing rolling step.

[0061] In the step of manufacturing the above billet, a billet can be manufactured comprising, in weight percent, C: 0.0001 to 0.0300%, Si: 0.001 to 3.000%, Mn: 0.001 to 0.500%, Al: 0.001 to 0.100%, P: 0.0001 to 0.0100%, S: 0.0001 to 0.0100%, N: 0.0001 to 0.0100%, and the remainder being Fe and other unavoidable impurities.

[0062] When heating the billet at the above heating temperature, it is heated to an austenite (g) single-phase region, so that after hot rolling, the microstructure can consist only of ferrite (a).

[0063] When finish rolling is performed at the above finish rolling temperature, a phase transformation from austenite to ferrite begins, and the austenite can be completely eliminated. In addition, workability during drawing can be ensured.

[0064] (S200) The stage of drawing wire

[0065] One embodiment of the present invention may include a step of drawing a wire at room temperature with a reduction rate of 59 to 93% so that the number density of shear bands is 11.4 bands / mm² or more. The shear band refers to a narrow region where deformation is locally concentrated and can mainly occur due to material non-uniformity, strength reduction, plastic deformation, etc. In the drawing step, when the wire is drawn at room temperature, a number of shear bands are generated within the microstructure. Since the phase transformation rate is rapid within the shear bands, the grains generated there absorb surrounding grains and become coarse, making them prone to exhibiting abnormal grain growth behavior. When used as a material for drive motor cores, reducing iron loss is important; since iron loss decreases as the grain size of the steel increases while other variables remain constant, it is better to increase the grain size after drawing and annealing heat treatment. Therefore, it is desirable to generate as many shear bands as possible within the microstructure during drawing. The number density of shear bands during the drawing stage may be 11.4 bands / mm² or higher. Preferably, it may be 29.0 bands / mm² or higher, and more preferably 35.0 bands / mm² or higher. If the reduction rate is too high, the shear bands generated during drawing may instead be destroyed by continuous deformation, resulting in a segmented structure with high dislocation density. Since this region has high stored energy, it becomes a nucleation-promoting site during annealing heat treatment, ultimately leading to the refinement of the recrystallized structure. Annealing heat treatment may be performed after drawing up to a reduction rate that maximizes shear band generation; however, if the reduction rate exceeds 93%, the generated shear bands begin to be destroyed, so it is desirable to keep it below this level. Conversely, if the reduction rate is too low, shear band generation is insufficient, and abnormal grain growth does not occur properly. Therefore, the reduction rate may be 59% or higher. Preferably, it is 69% or higher.

[0066] (S300) Step of heating the fresh wire and then performing annealing heat treatment

[0067] One embodiment of the present invention may include an annealing heat treatment step in which a drawn wire is heated to a range of (A1 - 110)°C to (A1 + 200)°C and maintained for at least 10 minutes. In the annealing heat treatment step after drawing, the annealing heat treatment temperature is a very important factor in determining the final microstructure. Since abnormal grain growth behavior does not appear if the heat treatment temperature is too low, the heat treatment can preferably be performed at (A1 - 110)°C or higher, more preferably at (A1 - 100)°C or higher. Conversely, since a phase transformation to austenite may occur if the temperature is too high, for stable operation, the heat treatment can preferably be performed at (A1 + 200)°C or lower, more preferably at A1°C or lower. Since the holding time at the corresponding temperature also has the effect of determining the final microstructure, just like the temperature, it can be maintained for at least 10 minutes.

[0068] [Example]

[0069] The present invention will be explained in more detail below through examples.

[0070] A billet having the composition as shown in Table 1 below was manufactured, the billet was heated at 1000°C to 1200°C, and the alloy was prepared by finish rolling at A1°C to (A1 + 100)°C.

[0071] In Table 1, Comparative Materials 1 to 4 each have C, P, S, and N contents that exceed the preferred range of the present invention. The A1 temperature is the result calculated using Thermo-Calc, a thermodynamic phase equilibrium calculation program. Alloy Composition (Wet%) A1 (℃) CSI Mn Al PSN Comparative Material 10.035 0.074 0.238 0.005 0.005 0.004 0.005719 Comparative Material 20.0052.526 0.115 0.005 0.013 0.008 0.004766 Comparative Material 30.0031.028 0.217 0.023 0.005 0.012 0.005935 Comparative Material 40.016 0.551 0.156 0.011 0.006 0.004 0.011735 Inventive Material 10.005 0.0680 .2640.0050.0080.0040.004844Inventive Material 20.0282.7410.0180.0830.0020.0030.005776Inventive Material 30.0141.0230.3120.0190.0090.0080.002793Inventive Material 40.0011.5640.1420.0920.0030.0030.0061039Inventive Material 50.0042.1170.4370.0010.0030.0020.003988

[0072] Table 2 shows the steel wire manufacturing conditions, the number density of shear bands of the steel wire after drawing, the average ferrite grain size of the steel wire after final annealing, and the magnetic flux density after final annealing. The average ferrite grain size in Table 2 was measured using the ASTM E112 method; measurements were taken at five random points located at 1 / 4 of the diameter of the manufactured steel wire, and the result is presented as the average value. Classification Alloy Steel Wire Manufacturing Conditions Steel Wire Shear Band Number Density After Drawing (Pieces / mm²) Steel Wire Average Ferrite Grain Size After Final Annealing (㎛) Steel Wire Magnetic Flux Density After Final Annealing B 50(T) Freshness Reduction Rate (%) Annealing Heat Treatment Temperature (°C) Annealing Heat Treatment Time (min) Number of Repetitive Cycles of Freshness and Annealing Heat Treatment (Times) Comparative Example 1 Comparative Material 18 37 15 30 12.8 19 1.64 Comparative Example 2 Comparative Material 27 77 50 20 19.5 17 1.59 Comparative Example 3 Comparative Material 35 98 50 10 16.9 36 1.68 Comparative Example 4 Comparative Material 46 87 30 25 18.4 7 31.65 Comparative Example 5 Inventive Material 25 77 60 30 22.4 8 6 1.68 Comparative Example 6 Inventive Material 27 76 60 30 29.7 10 9 1.71 Comparative Example 7 Inventive Material 3837605138.81331.70 Example 1 Inventive Material 19383015111.42611.76 Example 2 Inventive Material 29376030229.15521.81 Example 3 Inventive Material 37775015135.49421.78 Example 4 Inventive Material 46894510249.110751.84 Example 5 Inventive Material 592900202346.613131.99

[0073] Comparative Examples 1 to 4 each had C, P, S, and N contents exceeding the range of the present invention as shown in Table 1, and thus had low magnetic flux density after annealing heat treatment.

[0074] Comparative Example 5 had a drawing reduction rate of less than 59%. Accordingly, the number density of shear bands after drawing, the average grain size of the steel wire after the final annealing heat treatment, and the magnetic flux density after the final annealing heat treatment were not satisfied.

[0075] Comparative Example 6 had an annealing heat treatment temperature lower than (A1 - 110)℃. Accordingly, the number density of shear bands after drawing, the average grain size of the steel wire after the final annealing heat treatment, and the magnetic flux density after the final annealing heat treatment were not satisfied.

[0076] Comparative Example 7 had an annealing heat treatment time shorter than 10 minutes. Consequently, the number density of shear bands after drawing, the average grain size of the steel wire after the final annealing heat treatment, and the magnetic flux density after the final annealing heat treatment were not satisfied.

[0077] On the other hand, Examples 1 to 5, in which the composition and steel wire manufacturing conditions satisfied the scope of the present invention, satisfied the number density of shear bands after drawing, the average grain size of the steel wire after final annealing heat treatment, and the magnetic flux density after final annealing heat treatment, and it was confirmed that the magnetic properties were superior compared to the comparative example.

[0078] If you look at this by referring to the drawing, it is as follows.

[0079] FIG. 2 is a photograph showing the shear band of the steel wire after the drawing step of Comparative Example 3 among the experimental examples of the present invention, and FIG. 3 is a photograph showing the shear band of the steel wire after the drawing step of Example 2 among the experimental examples of the present invention.

[0080] Figure 2 shows the microstructure of the steel wire after the drawing step of Comparative Example 3 among the experimental examples of the present invention, where the arrow indicates the shear band.

[0081] As shown in Table 2, the shear band number density of Comparative Example 1 was 6.9 bands / mm², which is significantly lower than the lower limit of the shear band number density of 11.4 bands / mm² mentioned above, and the magnetic flux density of the steel wire after the final annealing heat treatment was found to be 1.68T.

[0082] On the other hand, Figure 3 shows the microstructure of the steel wire after the drawing step of Example 2 of the experimental examples of the present invention. As described in Table 2, the shear band number density of Example 2 is 29.1 bands / mm², and the magnetic flux density of the steel wire after the final annealing heat treatment is 1.81T.

[0083] As can be seen from the drawing, since the shear band number density after drawing satisfies the appropriate standard (11.4 bands / mm² or higher), it can be confirmed that the electromagnetic properties of the steel wire after the final annealing heat treatment are of an excellent level.

[0084] Although exemplary embodiments of the present invention have been described above, the present invention is not limited thereto, and those skilled in the art will understand that various changes and modifications are possible within the scope and concept of the claims set forth below.

Claims

1. In a wire rod comprising, in weight%, C: 0.0001 to 0.0300%, Si: 0.001 to 3.000%, Mn: 0.001 to 0.500%, Al: 0.001 to 0.100%, P: 0.0001 to 0.0100%, S: 0.0001 to 0.0100%, N: 0.0001 to 0.0100%, and the remainder being Fe and other unavoidable impurities, A wire rod having a shear band number density of 11.4 bands / mm² or more after being drawn at room temperature with a reduction rate of 59 to 93%.

2. In Claim 1, A wire rod having a shear band number density of 1.0 band / mm² or less after an annealing heat treatment in which the temperature is heated to a range of (A1 - 110)℃ to (A1 + 200)℃ and maintained for at least 10 minutes.

3. In Claim 2, A wire rod having an average ferrite grain size of 260㎛ or more after the above annealing heat treatment.

4. In Claim 1, A wire rod having an average ferrite grain size of 66㎛ to 200㎛ prior to the above-mentioned drawing.

5. In Claim 2, A wire having a magnetic flux density of 1.76T or higher after the above annealing heat treatment.

6. In Claim 1, A wire rod having a shear band number density of 29.0 or more after the above fresh post-transfer.

7. In Claim 1, A wire rod whose microstructure contains more than 99% ferrite by area fraction.

8. In wt%, C: 0.0001 to 0.0300%, Si: 0.001 to 3.000%, Mn: 0.001 to 0.500%, Al: 0.001 to 0.100%, P: 0.0001 to 0.0100%, S: 0.0001 to 0.0100%, N: 0.0001 to 0.0100%, the remainder comprising Fe and other unavoidable impurities, The average grain size of the ferrite is 260㎛ or larger, and Soft magnetic steel wire with a magnetic flux density of 1.76T or higher.

9. In Claim 8, Soft magnetic steel wire with a shear band number density of 1.0 bands / mm² or less.

10. In Claim 8, A soft magnetic steel wire whose microstructure contains more than 99% ferrite in area fraction.

11. A step of preparing a wire rod comprising, in weight%, C: 0.0001 to 0.0300%, Si: 0.001 to 3.000%, Mn: 0.001 to 0.500%, Al: 0.001 to 0.100%, P: 0.0001 to 0.0100%, S: 0.0001 to 0.0100%, N: 0.0001 to 0.0100%, and the remainder being Fe and other unavoidable impurities; A step of drawing the above wire at room temperature with a reduction rate of 59 to 93% so that the number density of shear bands is 11.4 bands / mm² or more; and A method for manufacturing a soft magnetic steel wire comprising an annealing step of heating the above-mentioned fresh wire to a range of (A1 - 110)℃ to (A1 + 200)℃ and maintaining it for at least 10 minutes.

12. In Claim 11, A method for manufacturing a soft magnetic steel wire in which, after the above-mentioned annealing heat treatment, the average grain size of the ferrite in the steel wire is 260 μm or more.

13. In Claim 11, A method for manufacturing a soft magnetic steel wire having a magnetic flux density of 1.76T or higher, after the above annealing heat treatment step.

14. In Claim 11, A method for manufacturing a soft magnetic steel wire in which, after the above-mentioned annealing heat treatment, the steel wire has a shear band number density of 1.0 band / mm² or less.

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