Heat treatment method and heat treatment furnace

Patent metadata

Field	Value
Publication number	US-12305248-B2
Application number	US-202217577809-A
Country	US
Kind code	B2
Filing date	Jan 18, 2022
Priority date	Aug 3, 2020
Publication date	May 20, 2025
Grant date	May 20, 2025

Abstract

The present disclosure relates to a heat treatment method and a heat treatment furnace that enable characteristics on an equal level to those when bluing processing is performed to be obtained without the bluing processing being performed in stress-relief annealing of a motor core. A heat treatment method according to one aspect is a heat treatment method in stress-relief annealing of a motor core. The heat treatment method includes an annealing step of annealing the motor core by using an exothermic converted gas as a furnace atmospheric gas, and a cooling step of cooling the motor core obtained in the annealing step, by using an exothermic converted gas as a furnace atmospheric gas, in a temperature range from a temperature in the annealing step to 500° C. at a cooling rate exceeding 600° C. per hour.

First claim

The invention claimed is:

1. A heat treatment furnace comprising:
a heating chamber configured to be supplied with an exothermic converted gas as a furnace atmospheric gas and to anneal a motor core, the heating chamber comprising a heater configured to control a temperature of the heating chamber to become a target temperature in annealing; and
a cooling chamber on a downstream side of the heating chamber communicating directly with the heating chamber, the cooling chamber being configured to be supplied with an exothermic converted gas as a furnace atmospheric gas, wherein
the cooling chamber comprises cooling means configured to cool the motor core passed through the heating chamber, in a temperature range from the temperature in annealing to 500° C. at a cooling rate which is a rate in a range equal to or higher than 650° C. per hour and equal to or lower than 700° C. per hour.

2. The heat treatment furnace according to claim 1 , further comprising:
a degreasing/preheating chamber upstream of the heating chamber.

3. The heat treatment furnace according to claim 1 , wherein the cooling chamber is configured such that an oxygen partial pressure within a system in the cooling chamber is
equal to or higher than a lower one of an oxygen balanced partial pressure of 3/2Fe+O 2 =1/2Fe 3 O 4 and an oxygen balanced partial pressure of 2Fe+O 2 =2FeO, and
equal to or lower than an oxygen balanced partial pressure of 4/3Fe+O 2 =2/3Fe 2 O 3 .

4. The heat treatment furnace according to claim 1 , wherein the cooling means includes a water cooling system.

Assignees

• Toyota Boshoku Kk
• Kanto Yakin Kogyo Co Ltd

Inventors

• Sugiyama Masaki
• Takahashi Shinichi
• Takahashi Kensuke
• TAKAHARA Kosuke

Classifications

• C21D11/005

  for cooling · CPC title

• C21D9/0068

  for particular articles not mentioned below · CPC title

• C21D9/005

  Furnaces in which the charge is moving up or down (for wire, strip C21D9/54) · CPC title

• C21D9/0006

  Details, accessories not peculiar to any of the following furnaces (control devices C21D11/00) · CPC title

• C21D9/00

  Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor · CPC title