Medium carbon steel sheet for cold working and method for manufacturing the same

Patent metadata

Field	Value
Publication number	US-9840750-B2
Application number	US-201114343580-A
Country	US
Kind code	B2
Filing date	Sep 22, 2011
Priority date	Sep 22, 2011
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

A medium carbon steel sheet for cold working that has a hardness of 500 HV to 900 HV when subjected to high-frequency quenching and a quick cooling to a room temperature is carried out. The medium carbon steel sheet includes, by mass %, C: 0.30 to 0.60%, Si: 0.06 to 0.30%, Mn: 0.3 to 2.0%, P: 0.03% or less, S: 0.0075% or less, Al: 0.005 to 0.10%, N: 0.001 to 0.01%, and Cr: 0.001 to 0.10%, the balance composed of Fe and inevitable impurities. An average diameter d of a carbide is 0.6 μm or less, a spheroidizing ratio p of the carbide is equal to or more than 70% and less than 90%, and the average diameter d (μm) of the carbide and the spheroidizing ratio p % of the carbide satisfy the expression d≦0.04×p−2.6.

First claim

The invention claimed is:

1. A medium carbon steel sheet for cold working that has a hardness of 500 HV to 900 HV in a case of being subjected to high-frequency quenching in which a temperature is raised at an average heating rate of 100° C./second, the temperature is held at 1,000° C. for 10 seconds, and a quick cooling to a room temperature is carried out at an average cooling rate of 200° C./second, the medium carbon steel sheet comprises,
C: 0.30 to 0.60 mass %,
Si: 0.06 to 0.30 mass %,
Mn: 0.3 to 2.0 mass %,
P: 0.030 mass % or less,
S: 0.0075 mass % or less,
Al: 0.005 to 0.10 mass %,
N: 0.001 to 0.01 mass %, and
Cr: 0.001 to 0.10 mass %,
and a balance composed of Fe and inevitable impurities, wherein
an average diameter d of a carbide is 0.37 μm or less, a spheroidizing ratio p of the carbide is equal to or more than 70% and less than 90%, and the average diameter d in μm of the carbide and the spheroidizing ratio p in % of the carbide satisfy d≦0.04×p−2.6.

2. The medium carbon steel sheet for cold working according to claim 1 ,
further comprises one or more of,
Ni: 0.01 to 0.5 mass %,
Cu: 0.05 to 0.5 mass %,
Mo: 0.01 to 0.5 mass %,
Nb: 0.01 to 0.5 mass %,
Ti: 0.001 to 0.05 mass %,
V: 0.01 to 0.5 mass %,
Ta: 0.01 to 0.5 mass %,
B: 0.001 to 0.01 mass %,
W: 0.01 to 0.5 mass %,
Sn: 0.003 to 0.03 mass %,
Sb: 0.003 to 0.03 mass %, and
As: 0.003 to 0.03 mass %.

3. The medium carbon steel sheet for cold working according to claim 2 ,
wherein a Cr content [Cr mass %] and a Mo content [Mo mass %] satisfy [Cr mass %]+[Mo mass %]/10<0.10.

4. The medium carbon steel sheet for cold working according to claim 1 or 2 ,
wherein the hardness prior to cold working is greater than or equal to 120 HV and less than 170 HV.

Assignees

• Takeda Kengo
• Abe Masayuki
• Tsukano Yasushi
• Aramaki Takashi
• Yamaguchi Shinichi
• Nippon Steel & Sumitomo Metal Corp

Inventors

• Takeda Kengo
• Abe Masayuki
• Tsukano Yasushi
• Aramaki Takashi
• Yamaguchi Shinichi

Classifications

• C22C38/32

  with boron · CPC title

• C22C38/06

  containing aluminium · CPC title

• C22C38/008

  containing tin · CPC title

• C22C38/58

  with more than 1.5% by weight of manganese · CPC title

• C22C38/50

  with titanium or zirconium · CPC title