Steel wire material and method for manufacturing same

Abstract

The steel wire material of the present invention contains 0.05 to 1.2% of C (mass %; same for the chemical components hereafter), 0.01 to 0.5% of Si, 0.1 to 1.5% of Mn, 0.02% or less (but not 0%) of P, 0.02% or less (but not 0%) of S, and 0.005% or less (but not 0%) of N, with the balance being iron and inevitable impurities. The wire material has a scale layer that is no thicker than 7.0 μm or less. The scale layer has an FeO percentage of 30 to 80 vol % and an Fe₂SiO₄ percentage of less than 0.1 vol %. The scale layer that is formed will not peel when cooled after hot rolling or during storage and transport, but will easily peel during mechanical descaling.

Description

TECHNICAL FIELD[0001]The present invention relates to a steel wire material and a method for manufacturing the same, and relates more specifically to a hot rolled steel wire material (hereinafter simply referred to as “wire material”) formed with a thin scale not peeling off during cooling after hot rolling and at the time of storage and transportation and easily removable by mechanical descaling, and a method for manufacturing the same.BACKGROUND ART[0002]A scale is formed normally on the surface of a wire material manufactured by hot rolling, and it is required to remove the scale before subjecting the wire material to secondary work such as drawing and the like. As such a scale removing method before secondary work, a batch type acid cleaning method was employed in prior arts, however, in recent years, from the viewpoints of the environmental pollution and cost reduction, a mechanical descaling (hereinafter referred to as MD) method has come to be employed. Therefore, the wire ma...

AI Technical Summary

Benefits of technology

[0016]In the steel wire material of the present invention, the FeO ratio is appropriately controlled to a predetermined range (30-80 vol %), and a thin (7 μm or less) scale is included. Accordingly, the scale does not peel off during cooling after hot rolling and at the time of storage and transportation, and generation of the rust can be prevented. Further, according to the present invention, because the scale easily peels off at the time of MD, sufficient peeling performance can be secured with a simple descaling device, adverse effects (a flaw on the surface of the wire material, defective lubrication and the like due to leaving the scale unremoved) are not exerted in secondary work such as drawing and the like, and the steel wire material of high quality can be provided. Also, because the scale loss is less, high yield can be maintained.

Problems solved by technology

However, Patent Literatures 1-5 described above have problems as described below.

Also, when the scale is thick, even when a bending strain is applied to the wire material by the MD method and the wire material surface is subjected to brushing, it is difficult to perfectly remove the scale.

More specifically, according to the MD method, unlike the batch type acid cleaning method, it is difficult to remove the entire scale evenly and stably, and even when the wire material formed with thick scale is subjected to MD, the surface of the wire material may occasionally be spotted with finely crushed scale powder.

When the remaining scale remaining locally thus increases, in the secondary work such as drawing and the like, problems such as occurrence of a flaw due to the defective lubrication, lowering of the lifetime of the dice and the like are caused.

Also, it is difficult to stably lower the boundary face roughness by the method of lowering the boundary face roughness such as Patent Literature 3, it is difficult to stably form the holes even by the method of forming holes inside the scale such as Patent Literatures 4, 5, and it is difficult to stably reduce the remaining scale amount according to either of these technologies.

Further, in these Patent Literatures 1-5, peeling off of the scale due to the compression stress generated during cooling is not considered at all, and there was a problem that the rust was generated in the wire material before MD by peeling off of the scale during cooling and at the time of storage and transportation.

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