Steel for Machine Structural Use

Patent metadata

Field	Value
Publication number	US-2019169723-A1
Application number	US-201716320651-A
Country	US
Kind code	A1
Filing date	Jul 27, 2017
Priority date	Jul 27, 2016
Publication date	Jun 6, 2019
Grant date	—

Abstract

Where, a content (mass %) of a corresponding element is substituted for each symbol of an element in Formula (1).

First claim

1 . A steel for machine structural use having a chemical composition consisting of, in mass %:
C: 0.15 to less than 0.30%, Si: 0.01 to 0.80%, Mn: 0.20 to 2.00%, P: 0.030% or less, S: 0.010 to 0.100%, Pb: 0.010 to 0.100%, Al: 0.010 to 0.050%, N: 0.015% or less, O: 0.0005 to 0.0030%, Cr: 0.50 to 2.00%, Ni: 0 to 3.50%, B: 0 to 0.0050%, V: 0 to 0.70%, Mo: 0 to 0.70%, W: 0 to 0.70%, Nb: 0 to less than 0.050%, Cu: 0 to 0.50%, Ti: 0 to 0.100%, and Ca: 0 to 0.0030%, with the balance being Fe and impurities, the chemical composition satisfying Formula (1), wherein, in the steel, a total number of specific inclusions which are any of MnS inclusions, Pb inclusions and composite inclusions containing MnS and Pb, and which have an equivalent circular diameter of 5 μm or more is 40 per mm 2 or more;
Mn/S≥8.0  (1)

where, a content (mass %) of a corresponding element is substituted for each symbol of an element in Formula (1).

2 . The steel for machine structural use according to claim 1 , wherein the chemical composition contains one or more types of element selected from a group consisting of:
Ni: 0.02 to 3.50%, B: 0.0005 to 0.0050%, V: 0.05 to 0.70%, Mo: 0.05 to 0.70%, W: 0.05 to 0.70%, Nb: 0.001 to less than 0.050%, Cu: 0.05 to 0.50%, and Ti: 0.003 to 0.100%.

3 . The steel for machine structural use according to claim 1 , wherein the chemical composition contains:
Ca: 0.0001 to 0.0030%.

4 . The steel for machine structural use according to claim 1 , wherein:
a ratio of a number of the composite inclusions with respect to the specific inclusions is 40% or more.

5 . The steel for machine structural use according to claim 2 , wherein the chemical composition contains:
Ca: 0.0001 to 0.0030%.

6 . The steel for machine structural use according to claim 2 , wherein:
a ratio of a number of the composite inclusions with respect to the specific inclusions is 40% or more.

7 . The steel for machine structural use according to claim 3 , wherein:
a ratio of a number of the composite inclusions with respect to the specific inclusions is 40% or more.

8 . The steel for machine structural use according to claim 5 , wherein:
a ratio of a number of the composite inclusions with respect to the specific inclusions is 40% or more.

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Hashimura Masayuki
• Egashira Makoto
• Toudou Shouji
• Iwahashi Takanori

Classifications

• C21C7/06

  Deoxidising, e.g. killing · CPC title

• C21C7/10

  Handling in a vacuum · CPC title

• C21C7/0006

  Adding metallic additives · CPC title

• B22D11/001

  of specific alloys · CPC title

• B22D11/124

  for cooling · CPC title