Vacuum annealing is a heat treatment process that uses a controlled vacuum environment and heat to alter the properties of metal components. The process is capable of providing a number of desirable results, including:
- Achieving the desired hardness to make them easier to work and shape
- Relieving stress to improve longevity and overall performance
- Preventing distortion and scaling
- Ensuring there are no decarburized areas, preserving carbon content
- Avoiding both intergranular and surface oxidation
- Leaving the parts with a clean, shiny surface that will not need washing after the annealing process
Vacuum annealing is suitable for a variety of materials, including stainless steels, titanium alloys, and tool steels.
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Equipment Used in Vacuum Annealing
The vacuum chamber used in the annealing process is a controlled environment where air and other gasses are removed to create a sterile space. These chambers can reach high temperatures and create and maintain a low-pressure or complete vacuum environment to ensure the annealed parts aren’t contaminated and have minimal defects. Inert gas is often used to quench the parts at a fixed rate to produce the necessary final results.
Steps in the Vacuum Annealing Process
At INCERTEC, annealing follows a fairly straightforward process. It always requires a vacuum furnace chamber that can heat to the required temperature and create an environment that is free of contaminants, with minimal or zero pressure. The steps include:
- Clean the parts of all surface contaminants, such as machining coolants and oils
- Correctly rack parts — outside of the furnace — to prevent accidental distortion during the process
- Load racks with the parts in the vacuum furnace chamber
- Engage the chamber to remove the atmosphere, creating the vacuum
- Heat and quench parts to in accordance with customer specifications
- Introduce inert gas at the end of the cycle to slowly cool the parts — this keeps them bright and contaminant-free
Best Metals for Vacuum Annealing
Many metals respond well to the annealing process. Some of the most common that we deal with are:
- Brass
- Copper
- Kovar
- Inconel
- PH steel
- Stainless steel
- Titanium
- Tool steels
Parts made of these materials that go through the annealing process have higher ductility and stability, allowing them to be worked again after the process. This enhances the reliability and overall precision when these materials are used in their end form, making them invaluable to many vital industries. Annealed metals are often found in engine and suspension parts in the automotive industry, aircraft frames and landing gears in the aerospace industry, semiconductors in the electronics industry and internal devices such as pacemakers in the medical industry.