Nitriding Treatment Method and Nitriding Treatment Apparatus

Patent metadata

Field	Value
Publication number	US-2022380881-A1
Application number	US-202017773750-A
Country	US
Kind code	A1
Filing date	Sep 4, 2020
Priority date	Nov 11, 2019
Publication date	Dec 1, 2022
Grant date	—

Abstract

The present invention provides a nitriding treatment method for forming a compound layer of ε phase (Fe2-3N) and γ′ phase (Fe4N) iron nitride excellent in wear durability in a steel material, from which a sliding member is formed, by short treatment, with a high thermal efficiency, with a reduced amount of used nitriding gas, and with a low environmental load. The nitriding treatment method of the present invention includes heating a sliding member made of a steel material at a temperature of 600° C. to 700° C. for a time of 1 to 25 minutes under an atmosphere of nitriding gas through high frequency induction heating or resistive heating, to form a compound layer of ε phase (Fe2-3N) and γ′ phase (Fe4N) iron nitride, the compound layer having a nitrogen content of higher than 4.5%, in a surface layer portion of the sliding member.

First claim

1 . A nitriding treatment method comprising:
heating a sliding member made of a steel material at a temperature of 600° C. to 700° C. for a time of 1 to 25 minutes under an atmosphere of nitriding gas through high frequency induction heating or resistive heating, to form a compound layer of ε phase (Fe 2-3 N) and γ′ phase (Fe 4 N) iron nitride, the compound layer having a nitrogen content of higher than 4.5%, in a surface layer portion of the sliding member.

2 . The nitriding treatment method according to claim 1 , wherein,
after the sliding member is heated, the sliding member is cooled.

3 . The nitriding treatment method according to claim 1 , wherein
the nitriding gas is supplied to a surface of the sliding member via natural convection or forced convection.

4 . A nitriding treatment apparatus comprising:
a nitriding chamber in which a sliding member made of a steel material is to be placed; a high frequency heating coil disposed in the nitriding chamber to subject the sliding member to high frequency heating; a vacuum pump that evacuates the nitriding chamber; a nitriding gas cylinder that supplies nitriding gas to the nitriding chamber; a nitrogen gas cylinder that supplies nitrogen gas to the nitriding chamber; a high frequency power source connected to the high frequency heating coil to energize the high frequency heating coil; and a forced convection generating unit disposed in the nitriding chamber to generate forced convection in the nitriding gas.

5 . The nitriding treatment apparatus according to claim 4 , wherein
the forced convection generating unit is a stirrer that stirs the nitriding gas.

6 . The nitriding treatment apparatus according to claim 4 , wherein
the forced convection generating unit is an up-down drive unit that moves the sliding member up and down.

7 . The nitriding treatment apparatus according to claim 4 , wherein
the forced convection generating unit is a rotary drive unit that rotates the sliding member.

Assignees

• Hitachi Ltd

Inventors

• Hatou Hisamitsu
• Shinagawa Kazuya
• Nakamura Keigo
• Kanemoto Hiroshi

Classifications

• C22C38/44

  with molybdenum or tungsten · CPC title

• C21D1/06

  Surface hardening · CPC title

• C22C38/04

  containing manganese · CPC title

• C23C8/26 Primary

  of ferrous surfaces · CPC title

• C21D1/767

  with forced gas circulation; Reheating thereof · CPC title