Vacuum Heat Treatment
Vacuum heat treatment: heat treatment in a hermetically sealed furnace under greatly reduced pressure to prevent chemical reactions with gases. The process guarantees clean surfaces and minimal distortion.
Physico-chemical mechanism of action
Vacuum heat treatment is carried out in a hermetically sealed furnace where the pressure is greatly reduced. This suppresses chemical reactions with gases such as oxygen and water vapor, which could normally occur during heat treatment. Reducing the pressure also prevents scaling reactions that could cause surface changes.
Metallurgical relevance & risks during welding
Vacuum heat treatment is especially important for steels with high carbon content or when using heavy alloys such as nickel and chromium. It prevents scaling reactions that could cause surface changes and loss of strength. However, an insufficient vacuum can lead to chemical reactions with gases, causing surface damage and reduced service life of the weld.
Workshop practice & instructions
To ensure successful vacuum heat treatment, the following steps must be observed:
• The furnace must be hermetically sealed and the pressure greatly reduced (typically below 10^-3 mbar).
• The treatment temperature must be precisely maintained to achieve the desired metallurgical properties.
• After treatment, the furnace must be cooled slowly to prevent scaling.
• The furnace must be regularly inspected and cleaned to ensure it remains hermetic.