Steel wire rod and manufacturing method of steel wire rod

Abstract

A steel wire rod according to an aspect of the present invention has a chemical composition in a predetermined range, in which a structure in a central part includes 80 area % to 100 area % of pearlite and a total of 0 area % or more and less than 20 area % of proeutectoid ferrite, proeutectoid cementite, martensite, and bainite; an average lamellar spacing of the pearlite in the central part is 50 nm to 100 nm; an average length of lamellar cementite in the central part is 1.9 μm or less; an average pearlite block size in the central part is 15.0 μm to 30.0 μm; a structure in a surface part includes 70 area % to 100 area % of the pearlite; and an average pearlite block size in the surface part is 0.40 times or more and 0.87 times or less the average pearlite block size in the central part.

Description

TECHNICAL FIELD OF THE INVENTION[0001]The present invention relates to a steel wire rod used as a material for an overhead power transmission line and various ropes, and a manufacturing method thereof.RELATED ART[0002]Aluminum conductor steel-reinforced cable (hereinafter, “ACSR”) is an electric wire having a configuration in which a zinc-coated steel wire is disposed at the center and hard aluminum wires are concentrically stranded around the steel wire, with each layer having alternating lays. In the related art, the steel wire for ACSR use has been mainly playing a role as a tension member for aluminum wires. As the steel wire for ACSR use, a steel wire obtained by drawing a pearlitic steel and performing zinc coating thereon, an aluminum-clad steel wire obtained by drawing a steel wire rod having an aluminum layer formed as the surface layer to improve corrosion resistance, and the like have been used in the related art.[0003]From the viewpoint of improving the power transmissio...

AI Technical Summary

Benefits of technology

The present invention is providing a steel wire rod that has high tensile strength and low electric resistivity, which enables the manufacturing of a steel wire with excellent torsional properties. The invention also provides a manufacturing method for this steel wire.

Problems solved by technology

However, the ACSR obtained by the technique disclosed in Patent Document 1 described above uses expensive carbon fiber as its core wire, so that a higher cost is incurred compared to an ACSR using a steel wire as its core wire.

In addition, in the technique disclosed in Patent Document 2, since the amounts of the alloying elements of the steel wire are reduced, it is difficult to secure the strength as the tension member of the steel core of the steel wire.

Furthermore, in the technique disclosed in Patent Document 3, N is solid soluted into lamellar ferrite by adding Ni and the electric resistance of the steel wire is increased, and thus, which is not preferable from the viewpoint of reducing the electric resistance.

Moreover, in general, there is a tendency that the tensile strength of a steel wire rod and the electric resistivity of the steel wire rod have a proportional relationship, so that it is difficult to manufacture a steel wire rod having both high tensile strength and high electric conductivity.

However, it has been difficult in the related art to impart sufficient electric conductivity to the steel wire rod having such a tensile strength for the above mentioned applications.

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