Excellent workability steel wire rod and method for production of same

Patent metadata

Field	Value
Publication number	US-10221464-B2
Application number	US-201515127142-A
Country	US
Kind code	B2
Filing date	Mar 20, 2015
Priority date	Mar 20, 2014
Publication date	Mar 5, 2019
Grant date	Mar 5, 2019

Abstract

The present invention provides a steel wire rod with stable workability. The steel wire rod has steel components containing, by mass %, C: 0.20 to 0.60%, Si: 0.15 to 0.30%, Mn: 0.25 to 0.60%, P: ≤0.020%, S: ≤0.010%, and a balance of Fe and unavoidable impurities, and an internal microstructure including cementite, in which by number ratio, 80% or more of the cementite in a cross-section vertical to a longitudinal direction of the wire rod has a short axis of 0.1 μm or less and a ratio of a long axis to the short axis, defined as an aspect ratio, of 2.0 or less.

First claim

The invention claimed is:

1. A steel wire rod comprising steel components including, by mass %, C: 0.20 to 0.60%, Si: 0.15 to 0.30%, Mn: 0.25 to 0.60%, P: ≤0.020%, S: ≤0.010%, and a balance of Fe and unavoidable impurities, and having an inside microstructure including cementite,
wherein by number ratio, 80% or more of the cementite in a cross-section vertical to a longitudinal direction of the wire rod has a short axis of 0.1 μm or less and a ratio of a long axis to the short axis, defined as an aspect ratio, of 2.0 or less,
wherein the inside microstructure comprises ferrite and bainite structures, and
wherein a ratio of lamellar-type structures contained in the inside microstructure is less than 5%.

2. The steel wire rod according to claim 1 further containing, in addition to said steel components, by mass %, one or more of Al: 0.06% or less, Cr: 1.5% or less, Mo: 0.50% or less, Ni: 1.00% or less, V: 0.50% or less, B: 0.005% or less, and Ti: 0.05% or less.

3. A method for production of a steel wire rod comprising heating a billet of a chemical composition according to claim 1 to 950° C. to 1080° C., supplying the billet to a wire rod rolling process to obtain a wire rod, coiling the wire rod in a temperature region of 750° C. to 900° C., then subjecting the wire rod to in-line heat treatment by a molten salt of 400° C. to 430° C., and ejecting the molten salt to the wire rod being dipped in the molten salt at a stirring flow rate of 0.5 m/s to 2.0 m/s in range.

4. A method for production of a steel wire rod comprising heating a billet of a chemical composition according to claims 2 to 950° C. to 1080° C., supplying the billet to a wire rod rolling process to obtain a wire rod, coiling the wire rod in a temperature region of 750° C. to 900° C., then subjecting the wire rod to in-line heat treatment by a molten salt of 400° C. to 430° C., and ejecting the molten salt to the wire rod being dipped in the molten salt at a stirring flow rate of 0.5 m/s to 2.0 m/s in range.

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Ooba Hiroshi
• Takahashi Yukihiro
• Nishikawa Yoshitaka

Classifications

• C21D8/06 Primary

  during manufacturing of rods or wires · CPC title

• C22C38/50

  with titanium or zirconium · CPC title

• C22C38/04

  containing manganese · CPC title

• C22C38/18

  containing chromium · CPC title

• C22C38/40

  with nickel · CPC title