Steel for Induction Hardening

Patent metadata

Field	Value
Publication number	US-2019300993-A1
Application number	US-201716316784-A
Country	US
Kind code	A1
Filing date	Jul 19, 2017
Priority date	Jul 19, 2016
Publication date	Oct 3, 2019
Grant date	—

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%, P: less than 0.020%, S: 0.025% or less, Al: more than 0.06% to 0.15%, N: 0.0020 to 0.0080%, O: 0.0015% or less, 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 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 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

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%; P: less than 0.020%; S: 0.025% or less; Al: more than 0.06% to 0.15%; N: 0.0020 to 0.0080%; O: 0.0015% or less; 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%; Ti: 0 to 0.050%; V: 0 to 0.05%; and Nb: 0 to 0.05%, with the balance being Fe and impurities, 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 . (canceled)

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

6 . The steel for induction hardening according to claim 1 , wherein the chemical composition contains one or more types selected from the group consisting of:
V: 0.01 to 0.05%; and Nb: 0.01 to 0.05%.

7 . The steel for induction hardening according to claim 2 , wherein the chemical composition contains one or more types selected from the group consisting of:
V: 0.01 to 0.05%; and Nb: 0.01 to 0.05%.

8 . The steel for induction hardening according to claim 3 , wherein the chemical composition contains one or more types selected from the group consisting of:
V: 0.01 to 0.05%; and Nb: 0.01 to 0.05%.

9 . The steel for induction hardening according to claim 5 , wherein the chemical composition contains one or more types selected from the group consisting of:
V: 0.01 to 0.05%; and Nb: 0.01 to 0.05%.

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Neishi Yutaka
• Miyanishi Kei
• Shiga Akira

Classifications

• C21C7/10

  Handling in a vacuum · CPC title

• C21D2211/009

  Pearlite · CPC title

• C22C38/40

  with nickel · CPC title

• C22C38/28

  with titanium or zirconium · CPC title

• C22C38/26

  with niobium or tantalum · CPC title