Steel plate for cold forging and process for producing same

Patent metadata

Field	Value
Publication number	US-8945719-B2
Application number	US-201113522578-A
Country	US
Kind code	B2
Filing date	Jan 25, 2011
Priority date	Jan 25, 2010
Publication date	Feb 3, 2015
Grant date	Feb 3, 2015

Abstract

This steel plate for cold forging includes a hot-rolled steel plate, wherein the hot-rolled steel plate includes: in terms of percent by mass, C: 0.13% to 0.20%; Si: 0.01% to 0.8%; Mn: 0.1% to 2.5%; P: 0.003% to 0.030%; S: 0.0001% to 0.008%; Al: 0.01% to 0.07%; N: 0.0001% to 0.02%; and O: 0.0001% to 0.0030%, with a remainder being Fe and inevitable impurities, an A value represented by the following formula (1) is in a range of 0.0080 or less, a thickness of the hot-rolled steel plate is in a range of 2 mm to 25 mm, and an area percentage of pearlite bands having lengths of 1 mm or more in a region of 4/10t to 6/10t when a plate thickness is indicated by t in a cross section of a plate thickness that is parallel to a rolling direction of the hot-rolled steel plate is in a range of not more than a K value represented by the following formula (2),

A value=O%+S%+0.033Al%  (1)

K value=25.5×C%+4.5×Mn%−6  (2).

First claim

The invention claimed is:

1. A steel plate for cold forging comprising:
a hot-rolled steel plate,
wherein the hot-rolled steel plate comprises: in terms of percent by mass,
C: 0.13% to 0.20%;
Si: 0.01% to 0.8%;
Mn: 0.6% to 2.5%;
P: 0.003% to 0.030%;
S: 0.0001% to 0.008%;
Al: 0.01% to 0.07%;
N: 0.0001% to 0.02%; and
O: 0.0001% to 0.0030%,
with a remainder being Fe and inevitable impurities,
an A value represented by following formula (1) is in a range of 0.0080 or less,
a thickness of the hot-rolled steel plate is in a range of 2 mm to 25 mm, and
an area percentage of pearlite bands having lengths of 1 mm or more is in a range of not more than a K value represented by following formula (2) in a region of 4/10t to 6/10t when a plate thickness is indicated by t in a cross section of a plate thickness that is parallel to a rolling direction of the hot-rolled steel plate,
A value=O%+S%+0.033Al%  (1)

K value=25.5×C%+4.5×Mn%−6  (2).

2. The steel plate for cold forging according claim 1 ,
wherein the hot-rolled steel plate further comprises, in terms of percent by mass, one or more selected from a group consisting of:
Nb: 0.001% to 0.1%;
Ti: 0.001% to 0.05%;
V: 0.001% to 0.05%;
Ta: 0.01% to 0.5%; and
W: 0.01% to 0.5%.

Assignees

• Abe Masayuki
• Takeda Kengo
• Yamamoto Shuji
• Tsukano Yasushi
• Yamaguchi Shinichi
• Nippon Steel & Sumitomo Metal Corp

Inventors

• Abe Masayuki
• Takeda Kengo
• Yamamoto Shuji
• Tsukano Yasushi
• Yamaguchi Shinichi

Classifications

• C22C38/04

  containing manganese · CPC title

• C22C38/02 Primary

  containing silicon · CPC title

• C22C38/24

  with vanadium · CPC title

• C22C38/005

  containing rare earths, i.e. Sc, Y, Lanthanides · CPC title

• C21D2211/005

  Ferrite · CPC title