Steel for induction hardening with excellent fatigue properties

Patent metadata

Field	Value
Publication number	US-9896749-B2
Application number	US-201314423754-A
Country	US
Kind code	B2
Filing date	Oct 18, 2013
Priority date	Oct 19, 2012
Publication date	Feb 20, 2018
Grant date	Feb 20, 2018

Abstract

A steel for induction hardening includes as a chemical composition, by mass %, C: 0.45% to 0.85%, Si: 0.01% to 0.80%, Mn: 0.1% to 1.5%, Al: 0.01% to 0.05%, REM: 0.0001% to 0.050%, O: 0.0001% to 0.0030%. Ca: 0.0050% or less as necessary, Ti: less than 0.005%, N: 0.015% or less, P: 0.03% or less, S: 0.01% or less, and the balance consists of Fe and impurities. The steel for induction hardening also includes a composition inclusion which is an inclusion containing REM, O, S, and Al, or an inclusion containing REM, Ca, O, S, and Al, to which TiN is adhered.

First claim

The invention claimed is:

1. A steel for induction hardening, comprising as a chemical composition, by mass%:
C: 0.45% to 0.85%;
Si: 0.01% to 0.80%;
Mn: 0.1% to 1.5%;
Al: 0.01% to 0.05%;
REM: 0.0001% to 0.050%;
O: 0.0001% to 0.0030%;
Ti: less than 0.005%;
N: 0.015% or less;
P: 0.03% or less;
S: 0.01% or less; and
the balance comprising Fe and impurities,
wherein the steel for induction hardening includes a composite inclusion which is an inclusion containing REM, O, S, and Al, to which TiN is adhered, and
the sum of a number density of TiN having a maximum diameter of 1 μm or more which independently exists without adhesion to the inclusion, and a number density of MnS having a maximum diameter of 10 μm or more is 5 pieces/mm 2 or less.

2. A steel for induction hardening, comprising as a chemical composition, by mass %:
C: 0.45% to 0.85%;
Si: 0.01% to 0.80%;
Mn: 0.1% to 1.5%;
Al: 0.01% to 0.05%;
Ca: 0.0050% or less;
REM: 0.0001% to 0.050%;
O: 0.0001% to 0.0030%;
Ti: less than 0.005%;
N: 0.015% or less;
P: 0.03% or less;
S: 0.01% or less; and
the balance comprising Fe and impurities,
wherein the steel for induction hardening includes a composite inclusion which is an inclusion containing REM, Ca, O, S, and Al, to which TiN is adhered, and
the sum of a number density of TiN having a maximum diameter of 1 μm or more which independently exists without adhesion to the inclusion, and a number density of MnS having a maximum diameter of 10 μm or more is 5 pieces/mm 2 or less.

3. The steel for induction hardening according to claim 1 or 2 , further comprising as the chemical composition, one or more kinds of elements selected from the group consisting of, by mass %:
Cr: 2.0% or less;
V: 0.70% or less;
Mo: 1.00% or less;
W: 1.00% or less;
Ni: 3.50% or less;
Cu: 0.50% or less;
Nb: less than 0.050%; and
B: 0.0050% or less.

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Hashimura Masayuki
• Miyazaki Masafumi
• Fujita Takashi
• Yamamura Hideaki

Classifications

• C21D2211/004

  Dispersions; Precipitations · CPC title

• C22C38/04

  containing manganese · CPC title

• C22C38/26

  with niobium or tantalum · CPC title

• C22C38/22

  with molybdenum or tungsten · CPC title

• C22C38/28

  with titanium or zirconium · CPC title