Steel for induction hardening

Patent metadata

Field	Value
Publication number	US-10808304-B2
Application number	US-201716316479-A
Country	US
Kind code	B2
Filing date	Jul 19, 2017
Priority date	Jul 19, 2016
Publication date	Oct 20, 2020
Grant date	Oct 20, 2020

Abstract

A steel for induction hardening according to the present invention includes a chemical composition consisting of, in mass percent: C: 0.58 to 0.68%, Si: 0.70 to 1.40%, Mn: 0.20 to 1.40%, Al: 0.005 to 0.060%, N: 0.0020 to 0.0080%, and Ca: 0.0005 to 0.005%, with the balance being Fe and impurities, and satisfies Formulae (1) to (3). The steel microstructure is made up of ferrite and by area fraction, 85% or more of pearlite. In the steel, a ratio of a number of composite inclusions to a total number of Al 2 O 3 inclusions and the composite inclusions that contain 2.0% or more of SiO 2 and 2.0% or more of CaO is 20% or more.

C+Si /7+ Mn /5+ Cr /9+ Mo /2.5≤1.05  (1)

C+Si /10+ Mn /20+ Cr /25≥0.70  (2)

Cr/Si ≤0.20  (3)

First claim

The invention claimed is:

1. A steel for induction hardening comprising
a chemical composition consisting of, in mass percent:
C: 0.58 to 0.68%;
Si: 0.70 to 1.40%;
Mn: 0.20 to 1.40%;
Al: 0.005 to 0.060%;
N: 0.0020 to 0.0080%;
Ca: 0.0005 to 0.005%;
Cr: 0 to 0.15%;
Cu: 0 to 0.50%;
Ni: 0 to 0.30%;
Mo: 0 to 0.20%;
B: 0 to 0.0040%; and
Ti: 0 to 0.050%;
with the balance being Fe and impurities,
the impurities including:
P: less than 0.020%;
S: less than 0.020%;
0: 0.0015% or less;
V: less than 0.01%; and
Nb: less than 0.01%,
and satisfying Formulae (1) to (3),

wherein
a steel microstructure is made up of ferrite and pearlite, where an area fraction of the pearlite is 85% or more, and
in the steel, a ratio of a number of composite inclusions to a total number of Al 2 O 3 inclusions and the composite inclusions is 20% or more, and the composite inclusions contain, in mass percent, 2.0% or more of SiO 2 and 2.0% or more of CaO, with the 99% or more of the balance being Al 2 O 3 ;
C+Si/ 7+ Mn/ 5+ Cr/ 9+ Mo/ 2.5≤1.05  (1)

C+Si/ 10+ Mn/ 20+ Cr/ 25≥0.70  (2)

Cr/Si≤ 0.20  (3)

where, symbols of elements in Formulae (1) to (3) are to be substituted by contents of corresponding elements (mass percent).

2. The steel for induction hardening according to claim 1 , wherein the chemical composition contains one or more types selected from the group consisting of:
Cr: 0.05 to 0.15%;
Cu: 0.03 to 0.50%;
Ni: 0.03 to 0.30%;
Mo: 0.01 to 0.20%; and
B: 0.0003 to 0.0040%.

3. The steel for induction hardening according to claim 1 , wherein the chemical composition contains Ti: 0.010 to 0.050%.

4. The steel for induction hardening according to claim 2 , wherein the chemical composition contains Ti: 0.010 to 0.050%.

Assignees

• Nippon Steel & Sumitomo Metal Corp
• Nippon Steel Corp

Inventors

• Neishi Yutaka
• Shiga Akira
• Miyanishi Kei

Classifications

• C22C38/54 Primary

  with boron · CPC title

• C22C38/44

  with molybdenum or tungsten · CPC title

• C22C38/20

  with copper · CPC title

• C22C38/00

  Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00) · CPC title

• C22C38/32

  with boron · CPC title