Hot forged product

Patent metadata

Field	Value
Publication number	US-10975452-B2
Application number	US-201616091828-A
Country	US
Kind code	B2
Filing date	May 20, 2016
Priority date	May 20, 2016
Publication date	Apr 13, 2021
Grant date	Apr 13, 2021

Abstract

There is provided a hot forged product having excellent wear resistance and fatigue strength even when the hot forged product is produced with a thermal refining treatment and a case hardening thermal treatment after hot forging omitted, and having a chemical composition consisting of, in mass %, C: 0.45 to 0.70%, Si: 0.01 to 0.70%, Mn: 1.0 to 1.7%, S: 0.01 to 0.1%, Cr: 0.05 to 0.25%, Al: 0.003 to 0.050%, N: 0.003 to 0.02% with the balance being Fe and impurities. The matrix at the depth of 500 μm to 5 mm from an unmachined surface of the forged product is a ferrite-pearlite structure, in which a pro-eutectoid ferrite area fraction is 3% or less or a pearlite structure, and the average diameter of pearlite colonies in the pearlite structure at the depth of 500 μm to 5 mm from the unmachined surface is 5.0 μm or less.

First claim

The invention claimed is:

1. A hot forged product having a chemical composition consisting of, in mass %,
C: 0.45 to 0.70%,
Si: 0.01 to 0.70%,
Mn: 1.0 to 1.7%,
S: 0.01 to 0.1%,
Cr: 0.05 to 0.25%,
Al: 0.003 to 0.050%,
N: 0.003 to 0.02%,
Ca: 0 to 0.01%,
Cu: 0 to 0.15%, and
Ni: 0 to 0.15% with the balance being Fe and impurities,
wherein a matrix at a depth of 500 μm to 5 mm from an unmachined surface of the forged product is a ferrite-pearlite structure, in which a pro-eutectoid ferrite area fraction is 3% or less or a pearlite structure,
an average diameter of pearlite colonies in the pearlite structure at the depth of 500 μm to 5 mm from the unmachined surface is 5.0 μm or less, and
the hot forged product exhibits a wear resistance,
wherein an amount of wear is less than or equal to 0.0080 g when a specimen having a size of 1.5 mm by 2.0 mm by 3.7 mm is subjected to a pin-on-disk wear test.

2. The hot forged product according to claim 1 ,
wherein the chemical composition contains, in mass %, Ca: 0.0005 to 0.01%.

3. The hot forged product according to claim 2 ,
wherein the chemical composition contains, in mass %, at least one selected from a group consisting of
Cu: 0.02 to 0.15%, and
Ni: 0.02 to 0.15%.

4. The hot forged product according to claim 3 ,
wherein the hot forged product is a crankshaft.

5. The hot forged product according to claim 2 ,
wherein the hot forged product is a crankshaft.

6. The hot forged product according to claim 1 ,
wherein the chemical composition contains, in mass %, at least one selected from a group consisting of
Cu: 0.02 to 0.15%, and
Ni: 0.02 to 0.15%.

7. The hot forged product according to claim 6 ,
wherein the hot forged product is a crankshaft.

8. The hot forged product according to claim 1 ,
wherein the hot forged product is a crankshaft.

9. The hot forged product according to claim 1 ,
wherein the hot forged product exhibits a fatigue strength of greater than 400 MPa
wherein a test bar of the hot forged product having a round cross-section formed from a parallel section of the hot forged alloy has a diameter of 8 mm and opposing grip sections each having a diameter of 12 mm.

Assignees

• Nippon Steel & Sumitomo Metal Corp
• Nippon Steel Corp

Inventors

• Nishihara Kison
• Kashiwara Yoshiyuki
• Tahira Hiroaki

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

• C22C38/58

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

• C22C38/00

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

• C22C38/42

  with copper · CPC title

• C22C38/02

  containing silicon · CPC title