JP4737662B2 - Method for manufacturing brass plated steel wire - Google Patents

Description

The present invention relates to a method for producing a brass-plated steel wire (hereinafter, also simply referred to as “manufacturing method”). Specifically, a steel wire having a desired wire diameter is obtained through a dry wire drawing step and a wet wire drawing step. The present invention relates to a method of manufacturing a brass-plated steel wire .

  Wire drawing performed to obtain a metal wire such as a steel cord from a metal raw material wire such as steel is an important process for finishing the metal wire to a predetermined wire diameter and imparting desired mechanical properties. is there. In general, the wire drawing method of a metal wire includes a dry wire drawing method using a dry lubricant and a wet wire drawing method using a wet lubricant. Usually, a dry wire drawing is performed on a raw material wire. Thus, after obtaining a wire having an intermediate wire diameter, a method is used in which a wire material having a final wire diameter is obtained by performing heat treatment on the wire and further performing wet wire drawing.

  Among such wire drawing processes, when only the dry wire drawing process is used, various studies have been made on the relationship between the true wire drawing strain, the processing depth, the amount of polax adhesion, and the like. Further, for example, in Patent Document 1, when a metal wire is drawn using a dry lubricant, the amount of adhesion of the polax film to the metal wire is prescribed, and a pass schedule for drawing is first set as a pass schedule. Even higher than the conventional isothermal pass schedule by defining the area reduction rate of each die of the die and the subsequent die from the die until the amount of adhesion of polax on the surface of the wire reaches a predetermined amount. There is described a technique for realizing a wire drawing method of a metal wire that can achieve a total area reduction or a high wire drawing rate and that is excellent in the workability of the entire metal wire.

Further, in Patent Document 2, in continuously drawing a plating-coated metal wire, after performing preliminary drawing for smoothing the plating surface of the metal wire, it is continuously wet using a plurality of dies. In the final wire drawing process, surface defects occur in the final wire drawing process by performing the first wire drawing using a higher concentration of liquid lubricant than the second and subsequent wire drawing. Is described in Japanese Patent Application Laid-Open No. 2003-260688. A predetermined final wet wire drawing is applied to the steel cord wire, and the processing depth of each wire drawing die is set within a predetermined range. Depending on the magnitude of the true wire drawing strain, the wire drawing dies with increasing or decreasing working depth are used as the die schedule, and the final wire drawing is performed, and the strength and strength of the surface layer and center of the wire The difference between the predetermined range , By combining a plurality of twisted wire obtained, it is described technique for realizing a rubber reinforcing steel cord having a complicated process without the need for high tensile strength and excellent fatigue resistance at a low cost. Furthermore, Patent Documents 4 to 6 also describe the wire drawing method in the wet wire drawing process for obtaining a high-strength strand.
Japanese Patent Laid-Open No. 11-226687 (Claims etc.) JP 2001-1030 A (Claims etc.) Japanese Patent Laid-Open No. 7-1973390 (claims, etc.) JP-A-7-258984 (Claims etc.) JP-A-7-305285 (Claims etc.) JP-A-10-325089 (Claims etc.)

  In wire drawing processing using both dry wire drawing and wet wire drawing as described above, it is the final wet wire drawing step that provides the wire diameter and tensile strength suitable for the use of the metal wire, but the preceding step It is considered that the wire drawing conditions of the dry wire drawing process may adversely affect the wet wire drawing process. That is, if the wire drawing conditions in the dry wire drawing process are inappropriate, micro cracks are formed inside the wire during processing, causing a central burst (CB) in the wet wire drawing process, and the surface and surface layer of the wire. In addition, since defects occur, there is also a problem that causes wear of the die to be accelerated.

Therefore, an object of the present invention is to suppress the occurrence of disconnection in the final wet drawing process by improving the drawing conditions when obtaining a desired steel wire through a dry drawing process and a wet drawing process. An object of the present invention is to provide a method for producing brass-plated steel wires with excellent productivity.

The present inventors have a result of intensive studies, by applying a predetermined drawing conditions in dry drawing process, it is possible to reduce the incidence of breakage in the final wet wire drawing process, thereby the brass-plated steel wire The inventors have found that productivity can be improved and have completed the present invention.

That, brass-plated steel wire production method of the present invention, with the wire of the intermediate wire diameter by dry drawing, this heat treatment is performed to obtain a steel wire of the final wire diameter by further wet-drawing, brass-plated steel In the wire manufacturing method, as the pass schedule in the dry wire drawing step, the wire drawing true strain ε = 2.0 or less, preferably the wire drawing true strain ε = 0.5 or later and ε = 2.0 or less. In addition, one or more passes having a processing depth of 80% or more are included.

  In the present invention, it is preferable that the pass at which the processing depth is 80% or more is a true wire drawing strain ε = 0.5 or later. Moreover, it is preferable to use a die satisfying an approach angle α in the range of 7 ° <2α ≦ 10 ° at least in the dry wire drawing step. In addition, when the true wire strain ε = 2.0 or more, it is preferable to gradually reduce the working depth of the die. The production method of the present invention is suitable when the steel wire having the final wire diameter has a tensile strength of 2940 MPa or more.

As described above, various studies have been made on the improvement of the wire drawing process. However, the conventional improvement technology is effective only for the corresponding process and improves the manufacturing defects in the wet wire drawing process. There is no known technology for improving the dry drawing process, which is the previous process, for the purpose of achieving the above.

According to the present invention, a steel wire when obtained by drawing by the dry drawing and wet-drawing, to improve the pass schedule in the dry drawing is before step, during the subsequent dry drawing It is possible to reduce the occurrence of internal defects, thereby reducing the disconnection rate in the wet wire drawing process and improving the productivity of the steel wire . In addition, when using a raw material wire that has defects such as segregation and inclusions and is inferior in quality, the disconnection rate in the wet wire drawing process is usually greatly increased, which greatly affects production efficiency. According to the improvement of the pass schedule in the dry wire drawing, it is also possible to suppress a rapid increase in the disconnection rate in the wet wire drawing process.

Hereinafter, preferred embodiments of the present invention will be described in detail.
The method for producing a brass-plated steel wire of the present invention is to obtain an intermediate wire diameter wire by dry drawing, heat-treat this, and further obtain a final wire diameter steel wire by wet drawing. It is characterized in that the pass schedule in the line process is defined in a predetermined manner.

  That is, in the disconnection that occurs in the wet wire drawing process, a fine defect (crack) already exists in the central part of the metal wire in the dry wire drawing process, which is the previous process, and the defect is in the subsequent wet wire drawing process. Some of the disconnections are caused by enlargement during wire drawing, but such disconnection is characterized in that unprocessed pearlite remains heat-treated at the tip of the fracture portion. When the wire drawing process in the dry wire drawing process is biased toward the wire surface layer portion, the compression to the center portion is insufficient and the tensile force becomes excessive, so that a condition is likely to cause a defect in the center portion.

  Therefore, in the present invention, by devising the pass schedule of the dry wire drawing process, the unevenness of processing is eliminated, more uniform processing is realized, and the occurrence of defects in the central portion of the wire is suppressed, thereby performing wet wire drawing. It is possible to reduce the occurrence of disconnection in the process. From the viewpoint of raw material wire, in recent years, the quality of steel manufacturers has improved, but the center segregation and inclusions in the wire have been reduced. However, it is not perfect yet, and the risk is further increased for overseas manufacturers. There is also a problem. However, according to the present invention, since it becomes possible to perform more uniform processing to the center of the wire, even when a raw material wire having a certain degree of segregation and inclusions is used, it has the same level of segregation and inclusions. Compared to the case where the conventional manufacturing method is applied to the raw wire, the risk of disconnection can be greatly reduced.

  Specifically, in the present invention, the pass schedule in the dry drawing process is performed before the wire reaches the true wire strain ε = 2.0, preferably after the true wire strain ε = 0.5. In this case, before reaching ε = 2.0, one or more, preferably 2 to 3 passes are provided at a machining depth of 80% or more, preferably 90 to 100%. By applying a pass schedule that satisfies the above conditions to the dry wire drawing process, it is possible to uniformly process the wire without unevenness, suppressing the occurrence of defects at the center, and the final wet wire drawing process It is possible to reduce the disconnection in the case.

Here, in the present invention, the wire drawing true strain ε is represented by the following general formula (1),
ε = 2ln (d ₀ / d ₁ ) (1)
Where ln represents the natural logarithm, d ₀ represents the wire diameter before drawing, and d ₁ represents the diameter of the wire after drawing. Moreover, since the processing depth of a wire changes with the area reduction rate in each die and the approach angle α of each die, it can be defined by the relationship with the approach angle α. As shown in FIG. 1, the distance from the surface of the wire 1 exiting the die 10 to the center of the wire 1 is Y, and the portion where the wire 1 is in contact with the approach portion of the die 10 at the approach angle α is the bottom. When the distance from the vertex of the equilateral triangle to the surface of the wire 1 on the die exit side is X, the processing depth is represented by (X / Y) × 100. If the incoming wire diameter is φA and the outgoing wire diameter is φB, then X = [(φA−φB) / 2] / [tan (π / 4 + α) −1] and Y = φB / 2. This processing depth is a measure for simply estimating the degree of deformation of the wire during wire drawing. For example, when the approach angle α is 4.5 ° and the area reduction rate is 27.06%, the processing depth is 100%. Therefore, in order to realize the processing depth according to the present invention, the approach angle α is in the range of 7 ° <2α ≦ 10 °, particularly 8 ° ≦ 2α ≦ 10 °, at least as a die used in the dry wire drawing process. It is preferable to use a satisfactory one.

  In addition, the strength of the wire increases as the degree of wire drawing increases, but the strength suddenly increases from around the true wire strain ε = 2.0, so that heat generation during wire drawing increases and the wire becomes brittle. There is a risk of becoming. For this reason, it is preferable to gradually reduce the working depth of the die when the true wire drawing strain ε = 2.0 or more. On the other hand, when the wire drawing true strain ε is less than 2.0, the strength of the wire is moderately increased. Therefore, it is preferable to increase the processing depth of the die from the viewpoint of processing the inside more uniformly.

In the production method of the present invention, other production conditions are not particularly limited as long as the drawing conditions in the dry drawing step are satisfied, and can be appropriately set according to a conventional method. For example, after obtaining a wire with a predetermined intermediate wire diameter from a raw material wire by a dry wire drawing process according to the above wire drawing conditions, the wire is subjected to patenting (heat treatment) and brass plating treatment to obtain a desired final wire diameter. What is necessary is just to use for the wet wire-drawing process for obtaining a wire. The production method of the present invention is suitable when the wire having the final wire diameter has a tensile strength of 2940 MPa (300 kgf / mm ² ) or more, particularly 3230 to 4700 MPa.

Hereinafter, the present invention will be described in more detail with reference to examples.
(Examples 1 and 2 and conventional example)
A high carbon steel wire rod having a diameter of 5.5 mm containing 0.8% by weight of carbon was subjected to dry drawing to a diameter of 3.1 mm, and then the three types of pass schedules A to C (Table 1 below) 2 (a) to (c), respectively), and further dry-drawn to a diameter of 1.72 mm (intermediate wire diameter).

  After applying the patenting and the brass plating treatment to the obtained intermediate wire diameter, two kinds of pass schedules (1) and (2) shown in Table 2 below (FIGS. 3A and 3B) , Respectively, was used for wet drawing to a diameter of 0.28 mm. Table 3 below shows the disconnection rate in the wet wire drawing and the evaluation result of the fracture surface thereof, together with the combinations of the dry wire drawing pass schedule and the wet wire drawing pass schedule of each example and the conventional example. The disconnection rate is represented by an index with the combination of Conventional Example C- (2) as 100, and the smaller the numerical value, the better the result. Also, “CB” in the table indicates “Central Burst”.

  As shown in Table 3 above, in Examples 1 and 2, the disconnection rate in wet wire drawing is reduced, and by satisfying the pass schedule in the wire drawing conditions of the dry wire drawing process according to the present invention, It was confirmed that the effect of reducing disconnection was obtained.

It is explanatory drawing which shows the calculation method of processing depth. (A)-(c) is a graph which shows the pass schedules AC in the dry-type wire drawing process of an Example, respectively. (A), (b) is a graph which shows the pass schedules (1) and (2) in the wet drawing process of an Example, respectively.

Explanation of symbols

1 Wire 10 Dice

Claims (5)

In the method for producing a brass-plated steel wire, a wire rod having an intermediate wire diameter is obtained by dry wire drawing, heat-treated, and a steel wire having a final wire diameter is obtained by wet wire drawing.
A method for producing a brass-plated steel wire, comprising, as a pass schedule in the dry drawing step, one or more passes having a working depth of 80% or more before the true wire drawing strain ε = 2.0.   2. The pass schedule in the dry drawing process includes one or more passes at which the processing depth is 80% or more before ε = 2.0 and after ε = 2.0. A method of manufacturing brass plated steel wire.   The method for producing a brass-plated steel wire according to claim 1 or 2, wherein a die satisfying an approach angle α in a range of 7 ° <2α ≦ 10 ° is used at least in the dry drawing step.   The method for producing a brass-plated steel wire according to any one of claims 1 to 3, wherein the processing depth of the die is gradually reduced at a wire drawing true strain ε = 2.0 or more.   The method for producing a brass-plated steel wire according to any one of claims 1 to 4, wherein the steel wire having the final wire diameter has a tensile strength of 2940 MPa or more.

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