JP6524745B2 - Steel wire manufacturing method - Google Patents

Description

  The present invention relates to a steel wire and a method of manufacturing the steel wire.

  In general, steel wire used as a strength member is formed by applying wire drawing with a die and in some cases intermediate patenting to a steel wire rod that has been made almost entirely in pearlite structure by hot rolling, patenting, etc. It is manufactured by plastic deformation and diameter reduction to the target diameter while securing. The steel wire obtains strength using work hardening by such plastic deformation in cold.

  The pearlite of the hot-rolled wire rod, which is a material for wire drawing, has a structure factor with a substantially uniform crystal orientation of ferrite, which is called a pearlite block or pearlite nodule, and is in the hot rolling stage or patenting process stage In the above, the crystal orientation of ferrite is completely random regardless of the rolling direction, and the orientation distribution is isotropic.

  However, by applying cold plastic working such as wire drawing, the orientation distribution of ferrite has anisotropy in which the <110> plane is strongly oriented in the longitudinal direction. Depending on the position of the material coordinate system, a texture is formed in the longitudinal direction, radial direction, and circumferential direction according to the processing process. Along with that, properties such as Young's modulus and plastic deformability by the degree of integration of a specific surface of the original single crystal become anisotropic.

  Conventionally, with regard to thin steel sheets obtained by cold rolling, a texture is formed using hot rolling, cold rolling, and heat treatment, and the rolling direction and mechanical in the width direction orthogonal to the rolling direction Many methods of controlling characteristics have been proposed.

  For example, in Patent Document 1 below, C: 0.005% to 0.04%, Si: more than 0.5% and 1.5% or less, etc. are contained by mass%, and further, Ti: 0.02 to 0 The steel material containing at least one selected from .20% and Nb: 0.02 to 0.20% is subjected to hot rolling at a rolling finish temperature of 850 ° C. to 950 ° C., 650 ° C. After taking up and acid pickling in the following, cold rolling and annealing are repeated twice to give a rigidity characterized by having a tensile strength of 540 MPa or more and a Young's modulus in a direction perpendicular to the rolling direction of 230 GPa or more. An excellent method for producing a thin steel sheet has been proposed.

  Moreover, in the following patent document 2, C: 0.005-0.04%, Si: 0.01-1.5%, Mn: 1.0-3.5%, P: 0.01 by mass%. ~ 0.020%, S: 0.0005 to 0.0400%, Al: 0.01 to 0.5% N: 0.0001 to 0.01%, the balance being from iron and unavoidable impurities Steel sheet having a rolling direction yield stress YP (L) and a width direction yield stress YP (C) of at least 400 MPa, | YP (C)-YP (L) | / YP (C) ≦ 0.04 A hot-rolled steel sheet satisfying the requirements is proposed.

JP, 2014-55310, A JP, 2013-87332, A

  On the other hand, with regard to a steel wire obtained by subjecting a hot-rolled wire or patenting material or the like mainly to cold drawing with a die, it is used by being embedded in a member as a reinforcing material in another member In applications, it is desirable to make the radial and longitudinal Young's modulus of the steel wire as consistent as possible with the member in which the steel wire is embedded. In the cold drawing with a conventional die, it is not possible to break away from the texture in which iron cubic <110> is strongly oriented in the drawing direction, and as a result, the longitudinal direction and diameter of the steel wire manufactured by the conventional method In the directions, Young's modulus (anisotropy of Young's modulus) greatly different from each other is expressed, and the characteristics are largely different in the longitudinal direction and the radial direction of the steel wire. In addition, even if the technology relating to a steel plate as proposed in Patent Document 1 and Patent Document 2 is simply applied to a steel wire, improving the anisotropy of Young's modulus in such a steel wire I can not do it.

  Therefore, the present invention has been made in view of the above circumstances, and the object of the present invention is to make the texture of the aggregate more anisotropic than that of a steel wire obtained only by the conventional die wire drawing processing. It is an object of the present invention to provide a steel wire having a more isotropic Young's modulus and excellent workability and a method of manufacturing the same.

  The present invention has been made to solve the above problems, and the summary of the present invention is as follows.

( 1 ) mass%, containing C: 0.75 to 1.1%, Si: 0.05 to 2.0%, Mn: 0.2 to 2.0%, the balance being from Fe and impurities Patenting step of performing patenting treatment in the range of 600 ° C. to 615 ° C. after heating the steel wire in the range of 1000 ° C. to 1070 ° C., and true strain within the range of 1.5 to 2.0 A swaging step to carry out the aging process, a peeling step to peel off the range of 0.1 mm to 0.2 mm in the direction of the central axis of the steel wire from the surface layer, and a die approach angle of 10 ° or more and less than 15 ° And a first wire drawing step of performing wire drawing within a range of 1.5 to 2.2 with true strain using a die of 15% to 25% with each step reduction rate; Die approach angle is 15 ° to 20 °, and each step reduction rate is 10% to 20 With% die, seen including a second drawing step of carrying out the drawing to the desired diameter, said steel wire after the second drawing step the center from the surface layer of the steel wire Ferrite with tilt angle difference within 5 ° from iron cubic <113> in a cylindrical region with a depth of 0.2 D to 0.4 D (D is the diameter of the steel wire) in the axial direction The fraction (Fm) in which is oriented in the longitudinal direction of the steel wire, and iron cubic <113> from the central axis of the steel wire to a direction of the surface layer of 0.1 D from <113> The ratio (Fm / Fc) of the fraction (Fc) with which the ferrite with the difference in inclination angle is oriented in the longitudinal direction of the steel wire is 1.1 to 3.5, and the Young's modulus (Ez) in the longitudinal direction The manufacturing method of the steel wire whose ratio (Ez / Er) with Young's modulus (Er) of radial direction is 0.75-1.25 .

  As described above, according to the present invention, the conventional die wire drawing is performed by optimizing the degree of integration of ferrite in the cross section of the steel wire by combining methods with different processing modes in an appropriate order and proportion. A steel wire having a more isotropic Young's modulus and excellent workability can be manufactured as compared to a steel wire manufactured only by processing. Therefore, in industry, the effect is extremely large.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  Under the circumstances as described above, the present inventors are directed to the material coordinates of the steel wire by combining the rolling reduction or patenting material that is the material with the cross-sectional reduction processing of different modes of swaging and wire drawing. Depending on the position, it has been found that different textures are formed than those produced by conventional manufacturing methods. When the present inventors repeated earnestly trial production based on such knowledge, they optimized the texture of the hot-rolled wire rod or patenting material as the material so as to withstand their processing, and the different modes as described above It is thought that the anisotropy of the accumulation degree of the specific surface of iron cubic crystal in the cross section can be optimized by combining the processing of in the proper order and proportion. As a result, a steel wire having a more isotropic texture in the longitudinal direction and the radial direction and having an isotropic Young's modulus than a steel wire obtained by reduction of area by only conventional die wire drawing. Succeeded in manufacturing. Hereinafter, the steel wire obtained based on such knowledge and its manufacturing method will be described in detail.

(About steel wire)
First, a steel wire according to an embodiment of the present invention will be described in detail.
The steel wire according to the present embodiment is a steel wire having a substantially circular cross section, which is manufactured by reducing the diameter of a hot-rolled wire or patenting material.

  The steel wire contains, by mass%, C: 0.75 to 1.1%, Si: 0.05 to 2.0%, Mn: 0.2 to 2.0%, and the balance is Fe and Iron cubic <113> in a cylindrical region with a depth of 0.2 D to 0.4 D (D is the diameter of the steel wire) from the surface layer toward the central axis direction of the steel wire The fraction (Fm) where ferrite with an inclination angle difference within 5 ° is oriented in the longitudinal direction of the steel wire and iron cubic in a cylindrical region with a depth of 0.1 D from the central axis of the steel wire to the surface direction The ratio (Fm / Fc) of the fraction (Fc) with which the ferrite having a tilt angle difference within 5 ° from crystal <113> is oriented in the longitudinal direction of the steel wire is 1.1 to 3.5, and the steel wire The ratio (Ez / Er) of the longitudinal Young's modulus (Ez) to the radial Young's modulus (Er) of the steel wire is 0.75 to 1.25 .

<Composition of steel wire>
First, the reasons for limitation of the components of the steel targeted for the steel wire according to the present embodiment will be described in detail. In the following description, “%” means “mass%” unless otherwise noted.

[C: 0.75% to 1.1%]
C has an effect of increasing the tensile strength after patenting treatment and increasing the rate of hardening by wire drawing work, and can increase the tensile strength of the steel wire with less drawing strain. If the C content is less than 0.75%, even if alloy elements are added, the tensile strength after patenting treatment is low, and since the wire drawing work hardening rate is also small, high strength steel wire I can not get it. On the other hand, when the C content exceeds 1.1%, pro-eutectoid cementite precipitates at austenite grain boundaries during patenting treatment, wire drawability deteriorates, and breakage occurs in the wire drawing process. It will be easier. Therefore, the content of C was limited to the range of 0.75 to 1.1%. The content of C is preferably 0.8% to 0.9%.

[Si: 0.05% to 2.0%]
Si is necessary for strengthening ferrite in pearlite and for deoxidation of steel, and is a very effective element for suppressing a reduction in strength due to heat. When the content of Si is less than 0.05%, the above effects can not be expected. On the other hand, when the content of Si exceeds 2.0%, surface decarburization tends to occur in the hot rolling process. Therefore, the content of Si is limited to the range of 0.05 to 2.0%. The content of Si is preferably 0.06% to 0.8%.

[Mn: 0.2% to 2.0%]
Mn is not only necessary for deoxidation and desulfurization, but is also an effective element for improving the hardenability of the steel and enhancing the tensile strength after patenting treatment. When the content of Mn is less than 0.2%, the above effect can not be obtained. On the other hand, when the content of Mn exceeds 2.0%, the above effect is saturated, and further, the processing time for completing the pearlite transformation at the time of patenting processing becomes too long, and the productivity is increased. descend. Therefore, the content of Mn is limited to the range of 0.2 to 2.0%. The content of Mn is preferably 0.25% to 0.4%.

[Other elements]
In the present embodiment, the balance of the above elements is Fe and impurities. Note that the steel wire according to the present embodiment is at least one element such as Cr, Cu, Ni, etc. as an unavoidable impurity or an element that improves various characteristics of the steel wire according to the present embodiment, You may contain in the range which does not impair the various characteristics of this invention.

<About the orientation of iron cubic>
Next, in the cross section of the steel wire according to this embodiment (the cross section in the direction orthogonal to the central axis of the steel wire), the reason for defining the orientation of the iron cubic by the distance from the surface layer or the center will be described. .

  As mentioned earlier, in the steel wire according to the present embodiment, iron cubic <113> to 5 in a cylindrical region with a depth of 0.2 D to 0.4 D in the direction of the central axis of the steel wire from the surface layer Iron cubic crystal in the fraction (Fm) in which ferrite with an inclination angle difference within 配 向 ° is oriented in the longitudinal direction of the steel wire and in a cylindrical region with a depth of 0.1 D from the central axis of the steel wire to the surface direction The ratio (Fm / Fc) of the fraction (Fc) with which the ferrite having a tilt angle difference within <5> from <113> is oriented in the longitudinal direction of the steel wire is 1.1 to 3.5.

  In the cross section of the steel wire, in a cylindrical region with a depth of 0.2 D to 0.4 D in the direction from the surface layer to the central axis, a ferrite having an inclination angle difference of 5 ° or less from <130> Has an angle difference within 5 ° from iron cubic <113> in the fraction (Fm) oriented in the longitudinal direction of the steel wire and the 0.1D cylindrical region in the direction from the central axis of the steel wire to the surface layer The ratio (Fm / Fc) of the fraction (Fc) in which the ferrite is oriented in the longitudinal direction of the steel wire is less than 1.1 is the range of the processing of the steel wire according to the present embodiment described in detail below. Within this, it can not occur at least within the range in which the present inventors conducted various experiments. Therefore, it was excluded from the range of the ratio according to the present invention.

  In addition, if the ratio (Fm / Fc) mentioned above exceeds 3.5, when the steel wire as a reinforcing material is subjected to a torsional stress, or if both a lateral stress and a tensile stress are simultaneously applied. When it receives, etc., the deformation due to the direction becomes large, a crack is generated between adjacent parts, and the steel wire is broken. For the above reasons, in the present embodiment, the range of the value of the ratio (Fm / Fc) is set to 1.1 to 3.5. The value of the above-mentioned ratio (Fm / Fc) is preferably 1.2 to 2.0.

  In addition, the measuring method of the orientation of iron cubic is not specifically limited, It is possible to utilize a well-known method. As such a measurement method, for example, a method using an orientation map of ferrite can be mentioned.

  In this method, a ferrite orientation map (Inverce Pole Figure (IPF) map) which is calculated by analyzing a crystal orientation of ferrite by EBSD (Electron Back Scattered Diffraction) pattern by an electron beam probe is used.

  More specifically, by using a known analysis application, crystal orientation information (positional coordinates and information of Euler angles with respect to the material coordinate system of the ferrite crystal) can be obtained for each pixel which is a unit of measurement. The orientation relationship between the material coordinate system of the steel wire and the ferrite crystal can be statistically aggregated from the crystal orientation information and the direction of cutting out the sample. By this, it is possible to determine the ratio of the number of pixels having information within 5 ° of the angle of formation from iron cubic <113> to the total number of pixels as described above. it can. Thereby, the two types of fractions Fm and Fc as described above can be obtained.

<On the ratio of Young's modulus in two directions>
Next, the ratio of Young's modulus in two directions realized by the steel wire according to the present embodiment will be described.
In the steel wire according to the present embodiment, by performing the processing described in detail below, the Young's modulus (Ez) in the longitudinal direction of the steel wire and the Young's modulus (Er) in the radial direction of the steel wire The ratio of (Ez / Er) is between 0.75 and 1.25. As apparent from the range of the ratio, in the steel wire according to the present embodiment, the Young's modulus (Ez) in the longitudinal direction and the Young's modulus (Er) in the radial direction have values close to each other, and isotropic Have sex. As a result, even when steel wires as reinforcements are subjected to various stresses, breakage of the steel wires can be efficiently suppressed, and the performance as reinforcements can be improved. It becomes possible. The value of the ratio (Ez / Er) of such Young's modulus is preferably 0.9 to 1.1.

  In addition, it does not specifically limit about the measuring method of the above-mentioned two-direction Young's modulus, It is possible to utilize a well-known measuring method. For example, the longitudinal Young's modulus (Ez) of a steel wire can be determined from the slope of the elastic deformation region showing a linear relationship in the displacement-load curve of a normal tensile test. In addition, the Young's modulus (Er) in the radial direction of the steel wire is obtained by pressing a predetermined cylindrical indenter perpendicularly to the steel wire, performing reduction with a predetermined load, and removing the load. It is possible to obtain from the inclination of the portion where the load curve is linear.

  The steel wire according to the present embodiment has been described above in detail.

(About the manufacturing method of steel wire)
Subsequently, a method of manufacturing a steel wire (a method of processing a steel wire) according to an embodiment of the present invention will be described in detail.
In the method of manufacturing a steel wire according to the present embodiment, (i) mass%, C: 0.75 to 1.1%, Si: 0.05 to 2.0%, Mn: 0.2 to 2.0 Patenting step of performing patenting treatment in the range of 600 ° C. to 615 ° C. after heating a steel wire containing 10% and the balance being Fe and impurities to the range of 1000 ° C. to 1070 ° C. A swaging step of carrying out a swaging process in the range of 1.5 to 2.0 by strain, and (iii) peeling off a range of 0.1 mm to 0.2 mm from the surface layer in the central axis direction of the steel wire And (iv) true strain in the range of 1.5 to 2.2, the die approach angle is 10 ° or more and less than 15 °, and the step reduction ratio is 15% to 25%. The first wire drawing step of performing wire drawing processing using a 90% die; (v) the die A second wire drawing step of performing wire drawing to a desired diameter using a die having a perforation angle of 15 ° to 20 ° and a step reduction rate of 10% to 20% each step; .

<Patenting process>
In the patenting process according to the present embodiment, the heating temperature in patenting is in the range of 1000 ° C. to 1070 ° C., and the temperature at which the patenting process is performed (patenting treatment temperature) is in the range of 600 ° C. to 615 ° C.

First, the reason for specifying the heating temperature in patenting will be described.
When the heating temperature in patenting is less than 1000 ° C., the diameter of the pearlite colony which is a region unit having the same orientation as the layered structure of the ferrite phase and the cementite phase, which is a feature of pearlite steel, becomes smaller. It is not suitable for a method of reducing surface area by combining complicated processes of different modes, and it is likely to cause defects during the process. Therefore, the heating temperature in patenting shall be 1000 degreeC or more.

  Also, if the heating temperature in patenting exceeds 1070 ° C., the unit called pearlite block or nodule, which is a region where the crystal orientation of ferrite is almost equivalent, becomes too coarse, and a defect is introduced in the center at the beginning of processing It is easy to do it and it inhibits the processability after this. Therefore, the heating temperature in patenting shall be 1070 degrees C or less.

  From the above reasons, in the method of manufacturing a steel wire according to the present embodiment, the heating temperature of patenting before cold working is set to 1000 ° C. or more and 1070 ° C. or less. The heating temperature in patenting is preferably 1020 ° C. to 1050 ° C.

Next, the reason for defining the patenting treatment temperature will be described.
When the patenting treatment temperature is less than 600 ° C., a portion which is not a part of layered pearlite tends to be generated, and the processability in the case of combining and processing plural different modes as in the present invention is inhibited. . Therefore, the patenting temperature is set to 600 ° C. or higher.

Also, if the patenting temperature exceeds 615 ° C., pro-eutectoid ferrite or pro-eutectoid cementite precipitates at the former austenite grain boundaries during pearlite transformation, and defects occur at such precipitation sites during surface reduction processing. It will be easier. Therefore, the patenting temperature is set to 615 ° C. or less.

For the above reasons, the patenting temperature is set to 600 ° C. or more and 615 ° C. or less in the method of manufacturing a steel wire according to the present embodiment. The patenting treatment temperature is preferably 610 ° C to 615 ° C.

  The details of the patenting treatment other than the above are not particularly limited, and the steel wire is heated using a known heating method, and the treatment is performed using a known heat bath. Good.

Swaging process
In the method of manufacturing a steel wire according to the present embodiment, following the patenting step as described above, a swaging step of performing a swaging process within a range of 1.5 to 2.0 in true strain is performed. .

First, the reason why the process immediately after patenting is the swaging process will be described.
When a pearlite structure is formed under the above-mentioned patenting conditions, if a wire drawing process is performed with a normal die immediately thereafter, a strong tensile stress acts on the central portion of the cross section, and a defect tends to occur in the central portion. As a result, it has been found that the possibility of disconnection in the subsequent processing is increased, which may cause the product to be unreliable.

  On the other hand, in the case of the swaging process, it is possible to form a structure that can withstand the wire drawing process with a die to be performed thereafter, while almost no tensile stress in the longitudinal direction is applied to the central portion. From this, the process immediately after patenting was a swaging process in which a strong tensile stress is not easily generated at the central portion.

Next, the reason which specified the quantity of the swaging process performed immediately after patenting is demonstrated.
If the amount of swaging process is less than 1.5 at the true strain calculated from the cross section reduction, the integrity of the central structure that can withstand the strong tensile stress of the central section in the subsequent die processing after the swaging step Can not form enough. Therefore, the amount of swaging is set to 1.5 or more in true strain.

  In addition, when the amount of swaging after the patenting is carried out with a true strain exceeding 2.0, cracks occur on the surface in the direction perpendicular to the direction in which the swaging is performed in the circumferential direction of the surface, The peel-off defined in the next step will exceed the removable range. Therefore, the amount of swaging is set to a true strain of 2.0 or less.

  For the reasons as described above, the amount of swaging to be carried out after the patenting step is in the range of 1.5 to 2.0 as the true strain calculated from the reduction in cross section. The amount of swaging is preferably 1.8 to 1.9 true strain calculated from the cross section reduction.

  The detailed conditions of the swaging process other than the above are not particularly limited, and may be implemented using a known swaging machine or the like.

<Peeling process>
In the method of manufacturing a steel wire according to the present embodiment, following the swaging step as described above, peeling is performed in a range of 0.1 mm to 0.2 mm from the surface layer toward the central axis direction of the steel wire. The process is performed.

The reason for defining the conditions for peeling after swaging will be described.
When swaging is performed, fine cracks are generated on the surface of the steel wire along the direction of the maximum shear stress of the surface in the direction perpendicular to the direction of the reduction. In order to remove this fine crack, the crack depth can not be removed uniformly unless the thickness of the peeling is at least 0.1 mm, considering the variation in wire diameter after swaging, the difference in diameter, etc. . On the contrary, the depth of surface cracks generated by swaging is usually 0.2 mm or less, and even if the surface is removed more than this, the yield of the product is reduced, so the upper limit of the skin peeling depth Was less than 0.2 mm.

  In addition, it does not specifically limit about the apparatus used for peeling processing, It is possible to use a well-known apparatus.

<First wire drawing process>
In the method of manufacturing a steel wire according to the present embodiment, following the peeling process as described above, the die approach angle is 10 ° or more and less than 15 °, and the step reduction rate is 15% to 25% in each step. The 1st wire-drawing process which implements a wire-drawing process in the range of 1.5-2.2 in true distortion is implemented using a dice | dies. The first wire drawing process is a wire drawing process using a die with a low approach angle of 10 ° or more and less than 15 °.

  Here, when the approach angle of the die used in the first wire drawing process is less than 10 °, the contact length between the die and the steel wire increases, and the power required for the wire drawing process is applied too much. Not desirable. Further, when the approach angle of the die is 15 ° or more, excessive tensile stress acts on the center portion of the steel wire, which is not preferable because defects such as cracks easily occur. Therefore, the approach angle of the die used in the first wire drawing process is 10 ° or more and less than 15 °.

Next, the reason for defining the low approach angle of 10 ° or more and less than 15 ° after the peeling process will be described.
When drawing with a low angle die with an approach angle of 10 ° or more and less than 15 ° with a true strain of less than 1.5, the center sufficient to withstand the wire drawing with a high angle die, which is the subsequent process The tissue integrity of the part can not be obtained, and a defect in the central part tends to occur. On the contrary, even if drawing with a low angle die is performed in a range where the true strain exceeds 2.2, the effect of imparting soundness to the central part is saturated, and subsequent texture control with a high angle die It is not possible to earn a reduction in area, and it becomes impossible to secure isotropy of the texture and Young's modulus of the steel wire.

  For the reasons as described above, the amount of wire drawing by a low-angle die having an approach angle of 10 ° or more and less than 15 ° after the peeling process was set to a range in which the true strain is 1.5 to 2.2. The amount of wire drawing by a low angle die is preferably 1.8 to 2.0 as a true strain calculated from a reduction in cross section.

  In addition, if the reduction in area at each step exceeds 25% in wire drawing at this stage, a strong tensile stress acts on the central portion, which is not preferable because the steel wire is broken. On the contrary, if the reduction in area in each step is less than 15% in the wire drawing at this stage, the effect of imparting the soundness to the central portion is reduced. From the above reasons, each step reduction rate in wire drawing with a low-angle die having an approach angle of 10 ° or more and less than 15 ° after the peeling step is set to a range of 15% to 25%. In addition, preferably each step reduction rate in the wire-drawing process by low angle dice | dies is 17%-18%.

<Second wire drawing process>
In the method of manufacturing a steel wire according to the present embodiment, the die approach angle is 15 ° to 20 ° and the step reduction ratio of each step is 10% to 20 subsequent to the first wire drawing process as described above. A second wire drawing process is performed, which performs wire drawing to the desired diameter using a% die. This second wire drawing process is a wire drawing process using a die with a high approach angle of 15 ° to 20 °.

First, the reason for defining a high approach angle of 15 ° to 20 ° in the final step will be described.
If the approach angle of the die at this stage is less than 15 °, the effect of making the anisotropy of the texture uniform is not sufficiently obtained, and the isotropic texture and Young's modulus as described above Is not preferable because it is impossible to obtain a steel wire. On the contrary, when the approach angle of the die exceeds 20 °, a strong tensile stress is generated at the center and the steel wire is broken during wire drawing. From the above, the approach angle of the die in the final step is set in the range of 15 ° to 20 °.

Next, the reason for defining each step reduction rate in the final process will be described.
If each step reduction rate by a high approach angle die exceeds 20%, a strong tensile stress acts on the center of the steel wire during wire drawing, which is not preferable because the steel wire tends to be broken. On the contrary, when each step reduction rate is 10 % or less, the effect of making the anisotropy of the texture uniform is not sufficiently obtained, and the steel wire according to the present embodiment as described above is used. I can not get it. From the above, each step reduction rate in the final step is set to 10% to 20 % . Each step reduction rate in the final step is preferably 17% to 18%.

  In the first wire drawing process and the second wire drawing process, the detailed conditions of the wire drawing process other than the above are not particularly limited, and can be carried out using known equipment. It is.

  As mentioned above, the manufacturing method of the steel wire concerning this embodiment was explained in detail.

  Below, the manufacturing method of the steel wire concerning this invention and a steel wire is concretely demonstrated, showing an Example and a comparative example. In addition, the Example shown below is only an example of the manufacturing method of the steel wire which concerns on this invention, and a steel wire, and the manufacturing method of the steel wire and steel wire which concerns on this invention is limited to the following example. Absent.

(Measurement of Young's modulus)
In addition, below, the longitudinal direction Young's modulus (Ez) of the steel wire was computed from the inclination of the elastic deformation area | region which shows a linear relationship in the displacement-load curve of a normal tension test. In addition, Young's modulus (Er) in the steel wire radial direction is made of WC-Co polished to Ra 1.0 μm or less according to JIS B 0601, and a cylindrical indenter having a radius of 0.8 mm is used, The cylindrical indenter was pressed against the steel wire perpendicularly, and after a pressure reduction of about 1 kg was performed, the load was loosely loaded, and the displacement-load curve obtained was calculated from the slope of the linear portion. In addition, the steel wire of evaluation object was left still on the WC-Co flat plate which was the same material as an indenter, and was ground by Ra 1.0 micrometer or less.

(Measurement of orientation of iron cubic <113>)
Next, a method of evaluating the anisotropy of texture from the ferrite orientation map used below will be described. The crystal orientation of the ferrite was calculated from the orientation map of the ferrite calculated by analysis of an EBSD (Electron Back Scattered Diffraction) pattern by an electron beam probe.

  More specifically, for example, in commercial applications such as TIM OIM-Analysis, crystal orientation information (positional coordinates and information on Euler angles with respect to the material coordinate system of ferrite crystal) is specified for each pixel which is a unit of measurement did. From the crystal orientation information obtained in this manner and the direction of cutting out the sample, the orientation relationship between the material coordinate system of the steel wire and the ferrite crystal was statistically collected. Thus, the ratio of the number of pixels having information within 5 ° to the total pixel number of the formation status of the texture for each minute part, that is, the angle from the iron cubic <113>, is calculated, and the two types of fractions It was Fm and Fc.

(Evaluation method of soundness of steel wire)
Next, a method of evaluating the soundness of the steel wire will be described.
When a steel wire is manufactured by a method deviating from the method of manufacturing a steel wire according to the present invention, a crack is generated in the center portion of the steel wire or in a surface layer of the steel wire, leading to breakage during manufacturing Remain to inhibit the characteristics of the product.

  In order to determine such a state, first, after swaging and peeling, the first step of soundness determination is performed. If the conditions of swaging or the conditions of peeling are inadequate, defects will remain on the surface, so if you fit a textile product like a hand with a hand and rub the steel wire, the fuzz that is visually distinguishable Remains on the surface. If no fluff is left on the surface of the steel wire after rubbed with a military hand, no surface defect has been formed at this stage, or removal of the defect is sufficient and disconnection in subsequent processes or reliability of steel wire products It can be judged that there is no loss of sex. In addition, what is applied to the steel wire when rubbing the steel wire surface is not particularly limited to a military hand, but it is desirable that it is a blended product containing cotton which is short in fiber length and easily fluffed.

  The second stage of soundness determination is performed after the final stage of wire drawing. The determination method is performed by observing the fractured surface of the tensile test residue. When wire drawing processing deviates from the manufacturing conditions of the steel wire according to the present invention, a defect called a chevron crack is easily generated at the center portion of the steel wire. When a steel wire with a chevron crack is subjected to a tensile test, it often becomes a residue having a characteristic conical fracture shape in the center of the test residue. On the contrary, when no defect occurs during manufacture, the central portion of the test residue often has a so-called cup-and-cone shape which forms a plane perpendicular to the longitudinal direction of the steel wire. From the above, immediately after the end of the final stage of wire drawing, a tensile test was conducted, and it was shown that the surface of the test residue was not conical, so that surface reduction could be properly performed without causing defects in the center. It can be determined that

(Test example)
Using the steel wire rod (diameter: 5.5 mm) having the chemical components (C, Si, the balance other than Mn is Fe and impurities) shown in Table 1 below, the manufacturing conditions shown in Table 1 Under the conditions, steel wires having the wire diameters shown in Table 1 were manufactured.

  Here, the value of “steel wire diameter” in Table 1 below is the final diameter of the manufactured steel wire, and the value of “true strain” in Table 1 below is the reduction in cross section before and after processing It is a value calculated from the size.

  Moreover, "surface property" of the column of "skin peeling" in the following Table 1 is an evaluation result of the first step of the above-mentioned soundness determination, and shows that ○ did not have fluff and x represents fluff It shows that there was. In addition, the “cut surface shape” in the column of “second wire drawing” in Table 1 below is the evaluation result of the second step of the above soundness determination, and ○ is a cup and cone type cut surface Indicates that the cross was a conical fracture surface.

  The obtained results are summarized in Table 1 below.

  As apparent from Table 1 above, No. The steels 1 to 8 were manufactured according to the method for manufacturing a steel wire according to the present invention, so that a texture satisfying the requirements for the steel wire according to the present invention is obtained, and the Young's modulus falls within the specified range. And, the remaining surface layer defects and the generation of central defects do not occur in the finished steel wire, which is an example corresponding to the present invention example.

  No. In No. 9 because the heating temperature in the patenting step is too low, the diameter of the pearlite colony becomes too small, and plastic deformation can not cope with a combination of complicated processing such as the method of manufacturing a steel wire according to the present invention. It is a comparative example which produced a defect in it. Conversely, no. No. 10 is a comparative example in which the pearlite block is too coarse because the heating temperature in the patenting step is too high, and a defect is introduced in the center at the initial stage of processing to inhibit the subsequent processability.

  No. 11, the transformation temperature of the patenting process is too low, so that a non-perlite structure is generated, and the processability for a combination of processing of a plurality of different modes such as the method of manufacturing a steel wire according to the present invention Is a comparative example which could not follow. Conversely, no. No. 12 is a comparative example in which primary ferrite or pro-eutectoid cementite precipitates at the prior austenite grain interface during pearlite transformation because the transformation temperature of the patenting step is too high, and a defect is generated during surface reduction processing.

  No. Comparative example 13 is that the structural integrity sufficient to withstand the strong tensile stress in the center due to the subsequent die processing can not be sufficiently formed due to the small amount of swaging processing, and defects tend to occur. It is an example. Conversely, no. No. 14 has cracks formed on the surface in the direction perpendicular to the reduction direction because the amount of swaging processing is too large, and the depth of cracks that can be removed in the peeling step specified in the next step is exceeded. It is a comparative example which inhibited the disconnection in the process and the surface quality of a product.

  No. No. 15 is a comparative example which was not able to remove uniformly the wrinkles which arose on the surface by swaging processing, since the depth of grinding in the peeling process was too shallow.

  No. In No.16, since the amount of wire drawing processing using a low approach angle die is too low, the structural integrity of the central part is not sufficiently obtained, and the wire drawing with a subsequent high approach angle die can be tolerated. This is a comparative example in which the tissue integrity as obtained is not obtained and a defect occurs in the central part. Conversely, no. No. 17 is that the structural integrity of the central part is saturated because the amount of wire drawing processing using a low approach angle die is too high, and the surface reduction rate of the texture control by the subsequent high angle die can be gained It is a comparative example which was not able to be carried out and was not able to secure the isotropy of the organization of steel wire, and Young's modulus.

  No. No. 18 is a comparative example in which a strong tensile stress acts on the center of a steel wire during wire drawing because the reduction in area of each step of the high approach angle die is too high, and the wire is broken.

  No. No. 19 is a comparative example in which a strong tensile stress acts on the center of the steel wire during wire drawing because the ratio of iron cubic crystals is out of the range, and the wire is broken.

  Thus, a steel wire manufactured according to the method of manufacturing a steel wire according to the present invention can have a more isotropic Young's modulus.

Although the preferred embodiments of the present invention have been described above in detail, the present invention is not limited to such examples. It is obvious that those skilled in the art to which the present invention belongs can conceive of various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also fall within the technical scope of the present invention.

Claims (1)

Steel wire containing, by mass%, C: 0.75 to 1.1%, Si: 0.05 to 2.0%, Mn: 0.2 to 2.0%, the balance being Fe and impurities And a patenting step of performing a patenting treatment in a range of 600 ° C. to 615 ° C. after heating to a range of 1000 ° C. to 1070 ° C .;
A swaging step of performing a swaging process within a range of 1.5 to 2.0 at true strain;
The peeling process which peels and processes the range of 0.1 mm-0.2 mm from surface layer toward the central axis direction of a steel wire,
Use a die with a die approach angle of 10 ° or more and less than 15 °, and a die reduction of 15% to 25% for each step reduction, and perform wire drawing within the range of 1.5 to 2.2 for true strain. The first wire drawing process to be performed;
A second wire drawing step of performing wire drawing to a desired diameter using a die having a die approach angle of 15 ° to 20 ° and a step reduction rate of 10% to 20% each;
Including
The steel wire after the second wire drawing process is
Iron cubic <113> in a cylindrical region with a depth of 0.2 D to 0.4 D (D is the diameter of the steel wire) from the surface layer toward the central axis direction of the steel wire A fraction (Fm) at which ferrite with an inclination difference within the range is oriented in the longitudinal direction of the steel wire, and iron cubic in a cylindrical region with a depth of 0.1 D from the central axis of the steel wire to the direction of the surface layer The ratio (Fm / Fc) of the fraction (Fc) with which the ferrite having a tilt angle difference within 5 ° from crystal <113> is oriented in the longitudinal direction of the steel wire is 1.1 to 3.5,
The manufacturing method of the steel wire whose ratio (Ez / Er) of Young's modulus (Ez) of a longitudinal direction and Young's modulus (Er) of a radial direction is 0.75-1.25.