Steel material for CVT sheave, CVT sheave, and method for manufacturing CVT sheave

Patent metadata

Field	Value
Publication number	US-11326244-B2
Application number	US-201716310946-A
Country	US
Kind code	B2
Filing date	Jul 18, 2017
Priority date	Jul 15, 2016
Publication date	May 10, 2022
Grant date	May 10, 2022

Abstract

Steel materials for continuously variable transmissions sheaves, and methods for manufacturing a continuously variable transmission sheaves, are provided. In the disclosed steel materials for continuously variable transmission sheaves, the steel materials satisfy the following expressions: 13.9≤Fn1≤15.5, and 1.20≤Fn2≤4.35 (in which Fn1=7×Cr−6×Si+4×Mn; and Fn2=Al×N×104).

First claim

The invention claimed is:

1. A steel material for a CVT sheave, the steel material consisting of the following components, in terms of mass percent (mass %):
carbon (C): 0.15 mass % or more and 0.20 mass % or less,
silicon (Si): 0.21 mass % or more and 0.30 mass % or less,
manganese (Mn): 0.70 mass % or more and 0.90 mass % or less,
sulfur (S): 0.010 mass % or more and 0.025 mass % or less,
chromium (Cr): 1.80 mass % or more and 1.90 mass % or less,
aluminum (Al): 0.015 mass % or more and 0.035 mass % or less,
nitrogen (N): 0.008 mass % or more and 0.017 mass % or less, and
optionally at least one member selected from the group consisting of copper (Cu) and nickel (Ni);

where
a remainder of the steel material is iron (Fe) and incidental impurities, and of the incidental impurities, phosphorus (P) and oxygen (O) contents are as follows:
phosphorus (P): 0.030 mass % or less, and
oxygen (O): 0.0020 mass % or less; wherein

the contents of the Si, Mn, and Cr components satisfy:
the above mass % ranges, and
the following expression (1):
Fn1=7×Cr−6×Si+4×Mn  (1)

where
Fn1 satisfies: 13.9≤Fn1≤15.5, and
“Cr,” “Si,” and “Mn” represent the Cr, Si, and Mn contents in mass %; and

the contents of the Al and N components satisfy:
the above mass % ranges, and
the following expression (2):
Fn2=Al×N×10 4   (2)

where
Fn2 satisfies: 1.20≤Fn2≤4.35, and
“Al” and “N” represent the Al and N contents in mass %.

2. The steel material for a CVT sheave according to claim 1 , wherein
the Cu is present at a content of no more than 0.30 mass %, and/or
the Ni is present at a content of no more than 0.25 mass %.

3. A CVT sheave formed by using a steel material for a CVT sheave as raw steel, wherein
Vickers hardness in a surface region from a sliding surface on which a CVT belt slides to 100 μm in a depth direction is 680 HV or more and 800 HV or less,
a volume fraction of retained austenite in the surface region is 13% or more and 28% or less, and
the steel material consists of the following components, in terms of mass percent (mass %):
carbon (C): 0.15 mass % or more and 0.20 mass % or less,
silicon (Si): 0.21 mass % or more and 0.30 mass % or less,
manganese (Mn): 0.70 mass % or more and 0.90 mass % or less,
sulfur (S): 0.010 mass % or more and 0.025 mass % or less,
chromium (Cr): 1.80 mass % or more and 1.90 mass % or less,
aluminum (Al): 0.015 mass % or more and 0.035 mass % or less, and
nitrogen (N): 0.008 mass % or more and 0.017 mass % or less, where
a remainder of the steel material is iron (Fe) and incidental impurities, and of the incidental impurities, phosphorus (P) and oxygen (O) contents are as follows:
phosphorus (P): 0.030 mass % or less, and
oxygen (O): 0.0020 mass % or less; wherein

the contents of the Si, Mn, and Cr components satisfy:
the above mass % ranges, and
the following expression (1):
Fn1=7×Cr−6×Si+4×Mn  (1)

where
Fn1 satisfies: 13.9≤Fn1≤15.5, and
“Cr,” “Si,” and “Mn” represent the Cr, Si, and Mn contents in mass %; and

the contents of the Al and N components satisfy:
the above mass % ranges, and
the following expression (2):
Fn2=Al×N×10 4   (2)

where
Fn2 satisfies: 1.20≤Fn2≤4.35, and
“Al” and “N” represent the Al and N contents in mass %.

4. A CVT sheave formed by using a steel material for a CVT sheave as raw steel, wherein
Vickers hardness in a surface region from a sliding surface on which a CVT belt slides to 100 μm in a depth direction is 680 HV or more and 800 HV or less,
a volume fraction of retained austenite in the surface region is 13% or more and 28% or less, and
the steel material consists of the following components, in terms of mass percent (mass %):
carbon (C): 0.15 mass % or more and 0.20 mass % or less,
silicon (Si): 0.21 mass % or more and 0.30 mass % or less,
manganese (Mn): 0.70 mass % or more and 0.90 mass % or less,
sulfur (S): 0.010 mass % or more and 0.025 mass % or less,
chromium (Cr): 1.80 mass % or more and 1.90 mass % or less,
aluminum (Al): 0.015 mass % or more and 0.035 mass % or less,
nitrogen (N): 0.008 mass % or more and 0.017 mass % or less, and
at least one member selected from the group consisting of copper (Cu) and nickel (Ni), where, when present, the Cu is present at a content of no more than 0.30 mass %, and, when present, the Ni is present at a content of no more than 0.25 mass %, where
a remainder of the steel material is iron (Fe) and incidental impurities, and of the incidental impurities, phosphorus (P) and oxygen (O) contents are as follows:
phosphorus (P): 0.030 mass % or less, and
oxygen (O): 0.0020 mass % or less; wherein

the contents of the Si, Mn, and Cr components satisfy:
the above mass % ranges, and
the following expression (1):
Fn1=7×Cr−6×Si+4×Mn  (1)

where
Fn1 satisfies: 13.9≤Fn1≤15.5, and
“Cr,” “Si,” and “Mn” represent the Cr, Si, and Mn contents in mass %; and

the contents of the Al and N components satisfy:
the above mass % ranges, and
the following expression (2):
Fn2=Al×N×10 4   (2)

where
Fn2 satisfies: 1.20≤Fn2≤4.35, and
“Al” and “N” represent the Al and N contents in mass %.

5. A method for manufacturing a CVT sheave, comprising:
processing the steel material for a CVT sheave according to claim 1 into a predetermined shape; and
gas carburizing a processed workpiece with a carbon potential (CP) of 0.70 mass % or more and 1.10 mass % or less.

6. A method for manufacturing a CVT sheave, comprising:
processing the steel material for a CVT sheave according to claim 2 into a predetermined shape; and
gas carburizing a processed workpiece with a carbon potential (CP) of 0.70 mass % or more and 1.10 mass % or less.

7. The CVT sheave formed according to claim 3 , wherein the silicon (Si) mass percent is 0.25 mass % or more and 0.30 mass % or less.

8. The CVT sheave formed according to claim 4 , wherein the silicon (Si) mass percent is 0.25 mass % or more and 0.30 mass % or less.

9. The CVT sheave formed according to claim 3 , wherein the Vickers hardness is 720 HV or more and 800 HV or less.

10. The CVT sheave formed according to claim 3 , wherein the Vickers hardness is 720 HV or more and 800 HV or less.

Assignees

• Aisin Corp
• Nippon Steel & Sumitomo Metal Corp
• Nippon Steel Corp

Inventors

• Hattori Masashi
• Tsukuda Kazumichi
• Nozaki Hiroyuki
• Kasai Daisuke
• Watanabe Takuya
• Ohashi Tetsuya
• Toudou Shouji
• Shiga Akira

Classifications

• C21D1/06

  Surface hardening · CPC title

• C23C8/22 Primary

  of ferrous surfaces · CPC title

• C22C38/02

  containing silicon · CPC title

• C22C38/001

  containing N · CPC title

• C22C38/04

  containing manganese · CPC title