JPH09327718A - Production of high strength extra fine steel wire excellent in twisting value - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily obtain the extra fine steel wire of high strength and high ductility by executing cold drawing more than a prescribed value in true strain before final wet drawing to a high carbon steel wire rod. SOLUTION: A high carbon steel wire rod, in which sulphide is finely dispersed, the structure after controlled cooling is of pearite and C content is >=0.6%, is subjected to cold drawing by a true strain of >=3.0 before final wet drawing. While executing intermediate patenting in order to elongate sulphide as much as possible, cold drawing is required to be done by a true strain of >=3.0. Intermediate annealing is esirably limited to one time. By this method, sulphide is elongated higher than conventional one, when subjecting to gamma treatment, fine dispersion of sulphide finer than conventional one is obtained. Thus, by reducing the γ grain size at patenting treatment, the ductility of steel wire is improved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a steel cord,
The present invention relates to a method for manufacturing a wire rod used for manufacturing a high strength steel wire such as a hose wire.

[0002]

2. Description of the Related Art In general, a wire rod made of high carbon steel is processed to a diameter of 5 to 16 mm by hot rolling, and then subjected to adjustment cooling to obtain a fine pearlite structure.
Thereafter, a wire having a diameter of 1.0 to 1.8 mmφ is formed by cold wire drawing and intermediate patenting, then subjected to final patenting, and further wire-drawn to 0.1 mm.
It is a very fine high strength wire of 2 to 0.4 mmφ. These wires are made of steel cord,
Hose wire.

As a method of making fine pearlite colonies at the time of final patenting, a method of precipitating fine precipitates by adding Al or the like is generally used. It is not used for ultra-fine steel wire to make Further, as a method for achieving a finer pearlite colony without using fine precipitates or the like, there is a technique described in JP-A-3-240919. This is a technique of reducing the γ grain size before transformation at the time of patenting by hot working in order to obtain a high-strength ultrafine steel wire. However, this method requires a significant modification to the patenting device conventionally used, and has a problem that it cannot be used easily.

[0004]

The present invention has high strength,
In addition, it is an object of the present invention to provide a technique capable of easily reducing the γ particle size during the patenting treatment in order to obtain an ultrafine wire having high ductility.

[0005]

That is, the gist of the present invention is that sulfides are finely dispersed in steel and the structure after conditioned cooling is a pearlite structure and the C content is 0.6% or more. It is a method for producing a high-strength ultrafine steel wire with an excellent twist value, which is characterized in that a high-carbon steel wire rod is subjected to cold drawing before the final wet drawing with a true strain of 3.0 or more.

Hereinafter, the present invention will be described in detail. It was known that sulfides existed as inclusions in steel and had an effect of suppressing the growth of γ grains, but sulfides could not be finely dispersed so as to affect the suppression of crystal grains. In order to increase the effect of suppressing the crystal grains of the sulfide, it is necessary to finely disperse the sulfide having a particle size of 1 μm or less in the steel. For this reason, in the present invention, a method is used in which sulfides are finely dispersed in steel as much as possible, and in order to further finely disperse the sulfides, the sulfides are elongated by wire drawing. FIG. 1 shows the concept of the method for suppressing the growth of γ grains using sulfides.

In order to increase this effect, it is important to further expand the sulfide by increasing the working amount by wire drawing and to make finer sulfide dispersion.
For this purpose, it is necessary to improve the workability of the steel itself to be used. When it is possible to take a large drawing strain, finer dispersion of sulfide in steel can be realized.

In order to extend the sulfide as much as possible,
It is necessary to perform cold wire drawing at a true strain of 3.0 or more while performing intermediate patenting. Desirably, the intermediate annealing is performed only once. As a result, the sulfide is elongated more than before, and a finer dispersion of the sulfide can be obtained during the gamma treatment. FIG. 2 shows the relationship between the cold drawing amount and the γ grain size obtained under the same heating conditions.
It can be seen that the larger the cold drawing amount, the smaller the γ grain size.

When the γ grain size before transformation is small, the twist value of the final wire drawn from the pearlite structure obtained by the isothermal transformation is improved. The relationship between the γ particle size and the twist value is shown in FIG. By thus reducing the γ grain size during the patenting treatment, the ductility of the obtained steel wire can be improved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Table 1 shows the chemical components of the samples used. Test Steel A is a steel according to the present invention in which sulfides are finely dispersed. Specimen Steel B is a steel for comparison and has no fine dispersion of sulfide in the steel. Wires having a diameter of 1.5 mmφ were obtained by wire drawing using the wire rods having 5.5 mmφ and 7.0 mmφ of the test steels A and B. At this time, for both wire diameters, the intermediate LP is 3.0 mmφ
I put it in.

Next, these wires are connected to each other under the same conditions as 575.
A patenting treatment was carried out at a temperature of 12 seconds. After that, wire drawing was further performed to obtain a 0.20 mmφ ultrafine steel wire. The strength and the twist value at this time are shown in Table 2. Although there is no significant difference in strength, the twist value is highest when manufactured using the 7.0 mm wire rod of sample steel A according to the present invention. In addition, these 1.5 mmφ wires at 1000 ° C. for 30 s
Table 3 shows the measurement results of the γ particle size when heated. 7.0 mm using the test steel A manufactured according to the present invention
It can be seen that the γ grain size becomes the smallest when processing is performed from φ wire.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

[Table 3]

[0015]

According to the present invention, an ultrafine steel wire having high strength and high ductility can be easily obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of γ grain size refinement by fine sulfides.

FIG. 2 is a diagram showing a relationship between a wire drawing amount and a γ grain size.

FIG. 3 is a diagram showing a relationship between a γ grain size before transformation and a twist value.

Claims (1)

[Claims] 1. A high carbon steel wire rod in which sulfides are finely dispersed in steel and the structure after conditioned cooling is a pearlite structure and the C content is 0.6% or more. A method for producing a high-strength ultra-fine steel wire with an excellent twist value, characterized in that the wire drawing is carried out at a true strain of 3.0 or more.