For many materials heated in a non-vacuum furnace, in addition to generating oxides, hydrides, and nitrides, the materials heated in a non-vacuum electric furnace will also absorb gas and diffuse into the interior, which seriously deteriorates the performance of the material. These oxidization, reduction, decarburization, carbon increase, gettering, and even corrosion problems are sometimes difficult to avoid in a controlled atmosphere furnace or a salt bath furnace, and vacuum heat treatment furnaces can avoid these disadvantages in many cases.
Vacuum heat treatment is essentially heat treatment in a very thin vacuum furnace atmosphere. Gas analysis in a vacuum electric furnace shows that the remaining gas in the vacuum furnace is H2Q, O2, CO2, and organic vapors such as grease. Because the content of these gases in the vacuum furnace is very small, its partial pressure is very low, which is not enough to cause the treated material to undergo reactions such as oxidation, reduction, decarburization, and recarburization. Therefore, the chemical composition on the surface of the material and the original surface brightness can be maintained. constant.
High vacuum in a vacuum furnace has two characteristics:
1. The chemical activity of the high vacuum atmosphere is extremely low. Therefore, when the vacuum electric furnace is used for the heat treatment furnace, the reactions occurring at the interface between the gas phase and the solid phase, such as oxidation, reduction, decarburization, and carburization, will not affect the degree;
2. The high-vacuum atmosphere in the multi-purpose furnace changes the volume of the gas very quickly, which can cause the material to release dissolved gases or oxides to decompose. Because of these two characteristics of the high vacuum atmosphere in the vacuum furnace, in the high vacuum atmosphere of the vacuum electric furnace, the oxygen partial pressure is very low, and the oxidation is suppressed. Therefore, in order to achieve the purpose of no oxidation, the partial pressure of oxygen in the vacuum furnace must be lower than the decomposition pressure of the oxides.