Vacuum Furnace Services

Vacuum heat treatment is the process of thermally processing materials under vacuum. To prevent contamination or to enhance the physical, chemical, or metallurgical properties of the material being heat-treated.

Vacuum furnaces are specialized types of furnaces that are used for high-temperature heating processes in an environment that is free of air or other gases.

Vacuum is used inside the sealed vacuum chamber in which the heating takes place. A fully automated vacuum system is used to generate the needed vacuum. A control system allows the ability to monitor and adjust the vacuum level to perfectly suit the respective heating cycle and application.

For example, some materials will require degassing once they reach certain temperatures, therefore the control system will heat up and hold the product at these temperatures for a defined period of time to let the gas evolution take place.

The dimensioning and design of the vacuum pump is critical to ensure the pump can handle the gas load of both, the product and the furnace.

The clean environment prevailing under vacuum is ideal for many metallurgical processes such as brazing, diffusion bonding, sintering, and hardening.

Various advanced and complex materials like Titanium and Inconel as well as high-quality stainless steels and their alloys are processed under vacuum. This allows the process to create a product with a bright, oxide-free finish.

A vacuum furnace system usually consists of the following core components:

• A vacuum chamber used to maintain the vacuum environment.
• A hot zone is an insulated resistance heater used to heat materials to 1,200 °C for most applications and to over 2,000 °C for some specialized processes. The insulated resistance heater consists of a series of heating elements made from high-temperature materials such as Inconel, graphite, Molybdenum or Tungsten depending on the process temperature and application.
• The elements heat up by way of resistance to electrical current. To prevent heat losses inside the hot zone, a thermal insulation barrier is used suitable for both, vacuum and high-temperature environments.
• A vacuum system delivers the required vacuum. It mostly consists of a roughing pump, a vacuum booster pump, a diffusion pump and a vacuum holding pump.
• A gas quenching system is used to cool the product rapidly at the end of the cycle thus improving material properties or cycle times. The product can also be cooled by building the vacuum chamber described above as a pressure vessel. For cooling purposes, this vessel is filled with high-pressure gas at the end of the cycle.
• A digital control system based on Programmable Logic Controllers (PLC) and Supervisory Control and Data Acquisition (SCADA).
• A water cooling system that keeps the furnace cool during operation by way of an external and internal water jacket.

• Implement a preventive maintenance schedule that includes the vacuum pumps, replacing O-rings (especially on doors and moving seals), and performing daily leak checks. Also inspect exposed flange sealing surfaces and clean the furnace hot zone.
• Take care of repairs by patching elements or heat shields, replacing elements or layers of shielding, or replacing the entire hot zone.
• Monitor signs such as reduced efficiency, inconsistent temperatures, or frequent breakdowns. If your hot zone is beyond repair, it’s time for a replacement.

A well-maintained hot zone ensures reliable operation and consistent heat treatment results.

The vacuum level of a vacuum furnace plays a crucial role in its operation.

• Commercially available vacuum pumping systems can achieve vacuum levels as low as 1 × 10^(-11) torrs (equivalent to 1.3 × 10^(-11) mbar or 1.3 × 10^(-14) atm).
• These ultra-low vacuum levels are essential for processes such as annealing, brazing, sintering, and heat treatment.
• Vacuum furnaces maintain uniform temperatures within the range 800–3,000°C (1,500-5,400°F) while minimizing contamination from carbon, oxygen and other gases.