Vacuum pumps for heat treatment and vacuum furnaces

After loading, the furnace is evacuated, then the batch is heated, held and cooled. According to Leybold, the air-free furnace atmosphere prevents oxidation; Pfeiffer Vacuum names an oxygen-free atmosphere and uniform heating. Busch describes the process as changing the material properties in a vacuum furnace at high temperature – usually 1,200 °C in the hot zone.

That depends on the process. Pfeiffer Vacuum names 10 to 10⁻³ hPa for tempering, 10⁻¹ to 10⁻² hPa for normalising, 1 to 10⁻² hPa for low-pressure carburising, about 10⁻² to 10⁻³ hPa for plasma nitriding, about 10⁻³ hPa for hardening and 10⁻² to 10⁻⁵ hPa for vacuum heat treatment.

Leybold names SOGEVAC, TRIVAC, RUVAC, DRYVAC and SCREWLINE as well as the VARODRY family. Edwards names rotary vane and dry screw vacuum pumps as well as EH, Stokes, GV and E2S, and for vacuum furnaces nXRi and E2S. Atlas Copco names DWS and GLS, for industrial furnaces GVD and for plasma processes DWS VSD+. Busch names R5, MINK, COBRA and PANDA/PUMA, Pfeiffer Vacuum ACP, DuoVane, HiLobe, HiScroll and UnoLine Plus, and for annealing also A4, TORRI and COBRA BC/DS.

The manufacturers name both types. Edwards lists rotary vane and dry screw vacuum pumps, Atlas Copco the oil-lubricated GVD and GLS as well as the dry screw vacuum pumps DWS. Leybold names SOGEVAC and TRIVAC alongside the dry DRYVAC and SCREWLINE; for vacuum carburising, in which carbon-containing by-products condense easily, Leybold names DRYVAC with RUVAC WH/WSU and SCREWLINE.

For vacuum and plasma nitriding, Leybold names SOGEVAC and DRYVAC and points out the high gas load around the clock; the process produces a nitride layer. For plasma nitriding Pfeiffer Vacuum names about 10⁻² to 10⁻³ hPa – the vacuum makes the plasma possible. Edwards lists EXS for nitriding and plasma nitriding, Busch COBRA and PANDA/PUMA for nitriding and Atlas Copco DWS VSD+ for plasma processes, each without further description.

For vacuum carburising, Leybold names DRYVAC with RUVAC WH/WSU and SCREWLINE and points out that carbon-containing by-products condense easily. For low-pressure carburising (LPC) Pfeiffer Vacuum names 1 to 10⁻² hPa at 900–1,050 °C for controlled carbon diffusion. Busch lists carburising with COBRA and PANDA/PUMA, Edwards carburising with EXS, both without further description.

According to Leybold, the batch is heated and rapidly quenched; DRYVAC and SOGEVAC are named. For hardening Pfeiffer Vacuum names about 10⁻³ hPa at 800–1,000 °C and a clean atmosphere at high temperature. Busch names case hardening as an example of the low-oxygen furnace atmosphere.

Because there is hardly any oxygen in the furnace: the vacuum removes the air before the heating starts. Leybold describes the air-free furnace atmosphere that prevents oxidation, Edwards the oxygen-free environment; for tempering Pfeiffer Vacuum names oxide-free, reproducible heating, and for normalising less oxidation and uniform heat.

For the hot zone, Busch names usually 1,200 °C, and above 2,000 °C for special processes. Pfeiffer Vacuum names 150–650 °C for tempering, 800–1,000 °C for hardening, 900–1,050 °C for low-pressure carburising and 600–1,300 °C for vacuum heat treatment, for example in brazing, sintering or crystal growing.

In vacuum carburising, Leybold points out that carbon-containing by-products condense easily, and names DRYVAC with RUVAC WH/WSU as well as SCREWLINE for this; in nitriding, Leybold expects a high gas load around the clock and names SOGEVAC and DRYVAC. A separator or filter upstream of the pump retains dust and condensate.

A central system in a room of its own keeps noise and heat away from production and matches its output to the demand. Central vacuum systems are planned and built by Eugen Theis Vakuum, a company of the Ehrler & Beck group – more under Central Vacuum.

Yes. Ehrler & Beck offers original spare parts and accessories as well as maintenance and repair.