IP Library Granted Patent US 10,385,427
Granted Patent B2
US 10,385,427 · App. 15/533,227 · Granted Aug 20, 2019

Wire rod

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Quick Facts
Patent No.
US 10,385,427
App. No.
15/533,227
Granted
Aug 20, 2019
Kind
B2
Abstract

A wire rod according to an aspect of the present invention has a predetermined chemical composition, a solute N is 0.0015% or less, a structure in an area from a surface of the wire rod to a depth of ¼ of a diameter of the wire rod in a cross section thereof includes 90.0 area % or more of pearlite, and 0 to 10.0 area % in total of bainite and ferrite, a total amount of martensite and cementite in the area from the surface of the wire rod to the depth of ¼ of the diameter of the wire rod is limited to 2.0 area % or less, and the calculated maximum size of TiN-type inclusions in a surface layer area of the wire rod is 50 μm or less.

Claims (32)

1. A wire rod, comprising: in terms of mass %,

C: 0.75% to 1.2%;

Si: 0.10% to 1.4%;

Mn: 0.1% to 1.1%;

Ti: 0.008% to 0.03%;

S: 0.003% to 0.030%;

P: 0.03% or less;

N: 0.001% to 0.005%;

Al: 0% to 0.1%;

Cr: 0% to 0.6%;

V: 0% to 0.1%;

Nb: 0% to 0.1%;

Mo: 0% to 0.2%;

W: 0% to 0.5%;

B: 0% to 0.003%; and

a remainder comprising Fe and impurities,

wherein a solute N is 0.0015% or less,

wherein a structure in an area from a surface of the wire rod to a depth of ¼ of a diameter of the wire rod in a cross section thereof includes 90.0 area % or more of pearlite, and 0 to 10.0 area % in total of bainite and ferrite,

wherein a total amount of martensite and cementite in the area from the surface of the wire rod to the depth of ¼ of the diameter of the wire rod is limited to 2.0 area % or less,

wherein a part from the surface of the wire rod to a depth of 10% of the diameter of the wire rod is defined as a surface layer area of the wire rod,

wherein a maximum circle equivalent diameter of TiN-type inclusions included in visual field of 12 mm 2 in a cross section, which is parallel to a rolling direction and which includes a center of the wire rod, of the surface layer area is defined as an actual maximum size of TiN-type inclusions in the surface layer area of the wire rod,

wherein an estimate value of a maximum circle equivalent diameter of the TiN-type inclusions included in the surface layer area of the wire rod having a length corresponding to a coil of 2 tons, which is obtained by extreme value statistical processing a Weibull plot created by the actual maximum size of the TiN-type inclusions in 12 or more of the visual fields of the surface layer area of the wire rod, is defined as a calculated maximum size of TiN-type inclusions in the surface layer area of the wire rod,

wherein the calculated maximum size of the TiN-type inclusions in the surface layer area of the wire rod is 50 μm or less, and

wherein a sulfide which is distributed along a prior austenite grain boundary and has an average number density of 0.025/μm 3 or more and a grain size of 10 to 100 nm is included in the area from the surface of the wire rod to the depth of ¼ of the diameter of the wire rod.

2. The wire rod according to claim 1 , further comprising: in terms of mass %, one or more selected from the group consisting of

Al: 0.001% to 0.1%;

Cr: 0.03% to 0.6%;

V: 0.005% to 0.1%;

Nb: 0.005% to 0.1%;

Mo: 0.005% to 0.2%;

W: 0.010% to 0.5%; and

B: 0.0004% to 0.003%.

Assignments (2)
CHANGE OF NAME Recorded May 14, 2019
From: NIPPON STEEL & SUMITOMO METAL CORPORATION
To: NIPPON STEEL CORPORATION
Reel/Frame 049257/0828 →
ASSIGNMENT OF ASSIGNOR'S INTEREST Recorded Jun 6, 2017
From: MANABE, TOSHIYUKI; ISO, ARATA; MATSUI, NAOKI
To: NIPPON STEEL & SUMITOMO METAL CORPORATION
Reel/Frame 042609/0948 →