Patent ID: 9181600
Filing Date: 2015-11-10
Classification: C21D,F27B

Abstract:
1. A heat treatment method comprising: a cooling step in which a cooling liquid in mist form is supplied to a treatment object which has been heated and transported into a cooling chamber, the cooling liquid reaches the treatment object and vaporizes, and the treatment object is cooled by depriving the treatment object of heat corresponding to latent heat of vaporization of the cooling liquid; and an atmospheric pressure-controlling step in which an atmospheric pressure in the cooling chamber is controlled based on a temperature at which the cooling liquid in mist form is supplied into the cooling chamber, the temperature being lower than a boiling point of the cooling liquid, so that a temperature difference between the temperature at which the cooling liquid in mist form is supplied and the boiling point of the cooling liquid becomes constant; wherein the cooling chamber is formed inside a vacuum vessel that is configured to permit varying the atmospheric pressure in the cooling chamber by a gas supplied from outside the cooling chamber or expelling gas from the cooling chamber, and wherein the cooling step includes alternately repeating a first step in which the treatment object is cooled at a first mist density and a second step in which the treatment object is cooled at a second mist density that is less dense than the first mist density.