HEAT TREATMENT METHOD AND HEAT TREATMENT FURNACE.

Abstract

The present invention relates to a heat treatment method and a heat treatment furnace that allows obtaining characteristics at the same level as when bluing is performed, without the bluing process being carried out during stress-relieving annealing of a motor core. One heat treatment method according to one embodiment of the invention is a stress-relieving annealing method for a motor core. The heat treatment method includes an annealing step for annealing the motor core using an exothermic converted gas as the furnace atmosphere, and a cooling step for cooling the motor core obtained in the annealing step, using an exothermic converted gas as the furnace atmosphere, to a temperature range from the annealing stage temperature down to 500°C at a cooling rate exceeding 600°C per hour.

Claims

1-A heat treatment method in stress-relieving annealing of a motor core, wherein the heat treatment method comprises: an annealing step for annealing the motor core using a gas exothermically converted to atmospheric furnace gas; and a cooling step consisting of cooling the motor core obtained in the annealing step, by using a gas exothermically converted to atmospheric furnace gas, in a temperature range from a temperature in the annealing step to 500°C at a cooling rate greater than 600°C per hour.

2. The heat treatment method according to claim 1, wherein the cooling step is performed immediately after the reburning step.

3. The heat treatment method according to claim 1 or 2, wherein the cooling step includes cooling the motor core after undergoing the reburning step at 300°C.

4. The heat treatment method according to any of claims 1 to 3, wherein the cooling rate is a rate in the range of 650°C per hour or higher to 700°C per hour or lower.

5. The heat treatment method according to any of claims 1 to 4, wherein a partial pressure of oxygen within a system in the cooling step is equal to or greater than the lesser of a balanced partial pressure of oxygen of 3 / 2Fe + O2 = 1 / 2Fe3O4 and a balanced partial pressure of oxygen of 2Fe + O2 = 2FeO, and equal to or less than a balanced partial pressure of oxygen of 4 / 3Fe + O2 = 2 / 3Fe2O3.

6. The heat treatment method according to any of claims 1 to 5, comprising: a degreasing / preheating stage of degreasing and / or preheating the engine core before the burn-off stage.

7. A heat treatment furnace comprising: a heating chamber configured to be fed with a gas exothermically converted as furnace atmospheric gas and for annealing the core of an engine; and a cooling chamber configured to be fed with a gas exothermically converted as furnace atmospheric gas and for cooling the engine core passing through the heating chamber, in a temperature range from a burn-off temperature to 500°C at a cooling rate exceeding 600°C per hour.

8. The heat treatment furnace according to claim 7, wherein the cooling chamber is arranged on a downstream side of the heating chamber to communicate directly with the heating chamber.

9. The heat treatment furnace according to claim 7 or 8, wherein the cooling rate is in the range of 650°C per hour or higher and 700°C per hour or lower. CQRtnn / zznz / e / YiAi 10. The heat treatment furnace according to any of claims 7 to 9, further comprising: a degreasing / preheating chamber upstream of the heating chamber.

11. The heat treatment furnace according to any of claims 7 to 10, wherein the cooling chamber is configured such that the partial pressure of oxygen within a system in the cooling chamber is equal to or greater than the lesser of a balanced partial pressure of oxygen of 3 / 2Fe + O2 = 1 / 2Fe3O4 and a balanced partial pressure of oxygen of 2Fe + O2 - 2FeO, and equal to or less than a balanced partial pressure of oxygen of 4 / 3Fe + O2 = 2 / 3Fe2O3.