Patent ID: 8741061

Claim:
A vacuum carburization apparatus comprising: a heating chamber including a heater; and a cooling chamber including a first cooler, wherein the heater heats a workpiece in the heating chamber to a first temperature, carburizing gas is supplied into the heating chamber to carburize the workpiece in a state where the inside of the heating chamber is depressurized lower than a predetermined pressure, the supply of the carburizing gas is stopped to diffuse carbon from the surface to the inside of the workpiece, and the workpiece is quenched in the cooling chamber by the first cooler in a state where the workpiece is set to a second temperature, and wherein the heating chamber includes: a furnace disposed inside the heating chamber and surrounded by a heat insulating partition wall, and the furnace provided with a workpiece transfer door to allow the transfer of the workpiece along a transfer path, the workpiece transfer door being positioned in the transfer path; a second cooler including a first gas convection device disposed in the furnace; and a gas flow door provided in the furnace at a different position from the workpiece transfer door and outside the transfer path, and the gas flow door is configured to switch between a first state in which gas can be circulated in the heating chamber between the inside and outside of the furnace, the first state corresponding to a state in which the furnace is opened by disposing the gas flow door at an opening position thereof, and a second state in which gas can be convected only inside the furnace, the second state corresponding to a state in which the furnace is closed by disposing the gas flow door at a closing position thereof while a temperature of the furnace is maintained.