General situation of vacuum gas quenching furnace
The metal materials of the vacuum gas quenching furnace are heated in the air furnace. Due to the existence of oxygen, water vapor, carbon dioxide and other oxidizing gases in the air, the oxidation of these gases with the metal is easy to produce oxide film or oxide skin on the surface of the heated metal, and completely lose the original metal luster. At the same time, these gases also react with carbon in the metal to decarburize its surface. If the furnace contains carbon monoxide or methane gas, the metal surface will also be carburized. For Ti, Zr and insoluble metals W, Mo, Nb and Ta, which are very active in chemical properties, when they are heated in an air furnace, not only oxides, hydrides and nitrides will be generated, but also these gases will be absorbed and diffused to the inside of the metal, so that the performance of the metal materials will be seriously deteriorated. These disadvantages, such as oxidation, decarburization, carburization, inhalation and even corrosion, are sometimes unavoidable when heated in a controlled atmosphere furnace or salt bath furnace. In order to solve this problem, the usual method is to leave machining allowance before heat treatment of workpieces, and remove oxidation and decarburization layer after heat treatment.