Hot forged steel material

Patent metadata

Field	Value
Publication number	US-11261511-B2
Application number	US-201816758592-A
Country	US
Kind code	B2
Filing date	Oct 31, 2018
Priority date	Oct 31, 2017
Publication date	Mar 1, 2022
Grant date	Mar 1, 2022

Abstract

A hot forged steel material in the present embodiment includes a chemical composition that consists of, in mass %, C: 0.14 to 0.20%, Si: 0.20 to 1.00%, Mn: 1.00 to 1.90%, P: 0.030% or less, S: 0.030% or less, V: 0.16 to 0.30%, Al: 0.015 to 0.050%, N: 0.0050 to 0.0250%, Cr: 0.10 to 0.30%, Cu: 0 to 0.10%, and Nb: 0 to 0.10%, with the balance being Fe and impurities, and that satisfies Formula (1) and Formula (2), wherein a grain size number of ferrite in the steel is 9.0 or more, and an absorbed energy at −30° C. is 100 J or more in the Charpy impact test using a V notch specimen.0.36≤C+(Si+Mn)/6+(Cr+V)/5+Cu/15<0.68  (1)51/12×C−V≤0.52  (2)

First claim

The invention claimed is:

1. A hot forged steel material comprising a chemical composition consisting of, in mass %:
C: 0.14 to 0.20%;
Si: 0.20 to 1.00%;
Mn: 1.00 to 1.90%;
P: 0.030% or less;
S: 0.030% or less;
V: 0.16 to 0.30%;
Al: 0.015 to 0.050%;
N: 0.0050 to 0.0250%;
Cr: 0.10 to 0.30%;
Cu: 0 to 0.10%; and
Nb: 0 to 0.10%,
with the balance being Fe and impurities, and satisfying Formula (1) and Formula (2), wherein
a total area fraction of ferrite and pearlite in a microstructure in the hot forged steel material is 95.0% or more,
a grain size number of ferrite specified in JIS G 0551(2013) in the hot forged steel material is 9.0 or more, and
an absorbed energy at −30° C. is 100 J or more in the Charpy impact test conforming to JIS Z 2242(2005) using a V notch specimen:
0.36≤C+(Si+Mn)/6+(Cr+V)/5+Cu/15<0.68  (1)

51/12×C−V≤0.52  (2),

where symbols of elements in Formula (1) and Formula (2) are to be substituted by contents of corresponding elements (mass %).

2. The hot forged steel material according to claim 1 , wherein
the chemical composition contains one or more selected from the group consisting of
Cu: 0.01 to 0.10% and
Nb: 0.01 to 0.10%.

3. The hot forged steel material according to claim 1 , wherein a tensile strength TS conforming to JIS Z 2241(2011) is 600 MPa or more.

4. The hot forged steel material according to claim 2 , wherein a tensile strength TS conforming to JIS Z 2241(2011) is 600 MPa or more.

Assignees

• Nippon Steel Corp

Inventors

• Sueyasu Yoko
• Tahira Hiroaki
• Yoshino Ken
• Nishihara Kison

Classifications

• C21D8/00

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• C22C38/001

  containing N · CPC title

• C22C38/20

  with copper · CPC title

• C22C38/00

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

• C22C38/38 Primary

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