High Carbon steel wire material having excellent wire drawability and manufacturing process thereof

Abstract

A high carbon steel wire material which is made of high carbon steel as a raw material for wire products such as steel cords, bead wires, PC steel wires and spring steel, allows for these wire products to be manufactured efficiently at a high wire drawing rate and has excellent wire drawability and a manufacturing process thereof. This high carbon steel wire material is made of a steel material having specific contents of C, Si, Mn, P, S, N, Al and O, and the Bcc-Fe crystal grains of its metal structure have an average crystal grain diameter (Dave) of 20 μm or less and a maximum crystal grain diameter (Dmax) of 120 μm or less, preferably an area ratio of crystal grains having a diameter of 80 μm or more of 40% or less, an average sub grain diameter (dave) of 10 μm or less, a maximum sub grain diameter (dmax) of 50 μm or less and a (Dave / dave) ratio of the average crystal grain diameter (Dave) to the average sub grain diameter (dave) of 4.5 or less.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a carbon steel wire material which is made of high carbon steel as a raw material for wire products such as steel cords, bead wires, PC steel wires and spring steel, allows for these wire products to be manufactured efficiently at a high wire drawing rate and has excellent wire drawability. [0003] 2. Description of Related Art [0004] To manufacture the above wire products, wire drawing is carried out on a steel wire material as a raw material for the control of size and material (mechanical properties) in most cases. Therefore, the improvement of the wire drawability of a steel wire material is extremely useful for the enhancement of productivity and the like. When wire drawability is improved, many advantages such as the improvement of productivity by an increase in wire drawing rate and a reduction in the number of passes for wire drawing and also the extension of the service life ...

AI Technical Summary

Benefits of technology

[0008] It is an object of the present invention which has been made in the view of the above situation to provide a steel wire material having excellent wire drawability which makes it possible to increase the wire drawing rate and the area reduction rate and extend the service life of a die, attaching great importance to productivity, and a process capable of manufacturing the steel wire material efficiently.

[0013] Further, the process of the present invention is useful for the manufacture of a high carbon steel wire material having excellent wire drawability and the above characteristic properties.

[0016] According to the present invention, a high carbon steel wire material which has excellent wire drawability and can enhance productivity due to increases in wire drawing rate and area reduction rate and can extend the service life of a die and a process capable of manufacturing the high carbon steel wire material having excellent wire drawability surely and efficiently can be provided by specifying the contents of C, Si, Mn, P, S, N, Al and O in the steel, specifying the average crystal grain diameter and the maximum crystal grain diameter of the bcc-Fe crystal grains of its metal structure, preferably suppressing the area ratio of coarse crystal grains and further specifying the average sub grain diameter and maximum sub grain diameter of the above bcc-Fe crystal grains and the ratio of these.

Problems solved by technology

If scale remains on the surface of a steel wire material due to poor descalability, it causes the chipping of the die at the time of wire drawing.

However, the above prior arts place main emphasis on the improvement of wire breakage resistance under specific wire drawing conditions and rarely pay attention to the improvement of wire drawing rate, the reduction of the number of passes for wire drawing and the extension of the service life of a die from the viewpoint of wire drawability.

As previously disclosed, increases in wire drawing rate and the area reduction rate per pass lead to the deterioration of the ductility of wire products and the shortage of the service life of the die.

However, the effect of improving wire drawability to such an extent that increases in wire drawing rate and area reduction rate can be achieved at practical levels is not obtained yet from the above prior arts.

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