For tertiary metallurgy applications as e.g. VIM or VAR, Leybold developed industrial vacuum solutions which feature a durable and reliable design. Offering excellent performance data, they are ideally suitable for such demand applications.
Traditionally in these applications oil-sealed rotary vane or rotary piston vacuum pumps were used. Today, those are widely replaces by more dust resistant, dry compressing screw-type pumps.
To achieve the required high pumping speed at the low operation pressures these are put in serie with 1-2 stages of Roots-Booster pumps.
For process pressures in the 10-3 mbar range (or lower), the usage of oil-booster pumps is mostly necessary. This pump-type delivery a bench-mark pumping speed for this specific pressure range, thus ensuring highest steel quality.
Challenges to the vacuum system
- Dust in the process gas
- High gas inlet temperatures
- Residual humidity and aggressive gases
- Process pressures down to 10-4 mbar (depending on the specific alloy)
To protect the vacuum system, a dust filtration is required. As the dust particles are often pyrophoric, the filtration system must be designed accordingly. Successfully used filter designs therefore typically use "inert-gas blow-back cleaning" steps to clean the filter surface.
|Vacuum Induction Melting (VIM) is used to melt high grade steels or special metals via electromagnetic induction under vacuum. The induction furnace is located inside a vacuum chamber. Ladle sizes are typically 200 - 3000 kg. The molten metal is refined under vacuum until the precise melt chemistry is achieved. Impurities are removed by chemical reaction, flotation, disassociation, and volatilization.
The VIM process is used for example to produce stainless steels, superalloys, magnetic and battery alloys or high-grade non-iron metals.
|Vacuum Arc Remelting (VAR) is used to continuously remelt a consumable electrode via an arc under vacuum. High vacuum is maintained during the melting process to remove impurities and prevent oxide formation. The VAR process is used to improve the quality and purity of air-melted ingots or metals coming from the VIM process to produce clean, homogeneous metals with improved fatigue resistance and fracture strength.|