Cold-Wall Retort Furnaces up to 2400 °C

A wide variety of heating designs as well as a complete range of accessories provide for optimal retort furnace configurations even for sophisticated applications.

Process Control

Function and equipment

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The compact retort furnaces of the VHT product line are available as electrically heated chamber furnaces with graphite, molybdenum, tungsten or MoSiheating. A wide variety of heating designs as well as a complete range of accessories provide for optimal retort furnace configurations even for sophisticated applications.

The vacuum-tight retort allows heat treatment processes either in protective and reaction gas atmospheres or in a vacuum, subject to the individual furnace specs to 10-5 mbar. The basic furnace is suited for operation with non-flammable protective or reactive gases or under vacuum. The Hversion provides for operation under hydrogen or other flammable gases. Key of the specification up is a certified safety package providing for a safe operation at all times and triggers an appropriate emergency program in case of failure.

Alternative Heating Specifications

In general the following variants are available with respect to the process requirements:

VHT ../..-GR with Graphite Insulation and Heating

  • Suitable for processes under protective and reaction gases or under vacuum
  • Tmax 1800  °C, 2200  °C or 2400 °C (VHT 40/.. - VHT 100/..)
  • Max. vacuum up to 10-4 mbar depending on pump type used
  • Graphite felt insulation

VHT ../..-MO or VHT ../..-W with Molybdenum or Tungsten Heating

  • Suitable for high-purity processes under protective and reaction gases or under high vacuum
  • Tmax 1200  °C, 1600  °C or 1800  °C (see table)
  • Max. vacuum up to 10-5 mbar depending on pump type used
  • Insulation made of molybdenum rsp. tungsten radiation sheets

VHT ../..-KE with Fiber Insulation and Heating through Molybdenum Disilicide Heating Elements

  • Suitable for processes under protective and reaction gases, in air or under vacuum
  • Tmax 1800  °C
  • Max. vacuum up to 10-2 mbar (up to 1300  °C) depending on pump type
  • Insulation made of high purity aluminum oxide fiber
  • Exclusive use of insulation materials without categorization according to EC Regulation No. 1272/2008 (CLP)

Basic version

  • Standard furnace sizes 8 - 500 liters
  • Water-cooled retort made of stainless steel
  • Frame made of stable steel profiles, easy to service due to easily removable stainless steel panels
  • Housing of the VHT 8 model on castors for easy repositioning of furnace
  • Cooling water manifold with manual tap, automatic flow monitoring, open-loop cooling water system
  • Adjustable cooling water circuits with flowmeter and temperature indicator and overtemperature protection
  • Switchgear and controller integrated in furnace housing
  • Process control with controller P570
  • Over-temperature limiter with adjustable cutout temperature as temperature limiter to protect the furnace and load
  • Manual operation of the process gas and vacuum functions
  • Manual gas supply for one process gas (N2, Ar or non-flammable forming gas) with adjustable flow
  • Bypass with manual valve for rapid filling or flooding of furnace chamber
  • Manual gas outlet with overflow valve (20 mbar relative) for over-pressure operation
  • Single-stage rotary vane pump with ball valve for pre-evacuating and heat treatment in a rough vacuum to 5 mbar
  • Pressure gauge for visual pressure monitoring
  • Defined application within the constraints of the operating instructions

Additional equipment

Additional equipment gas management system

  • Manual gas supply for second process gas (N2, Ar or non-flammable forming gas) with adjustable flow and bypass
  • Mass flow controller for alternating volume flow and generation of gas mixtures with second process gas (only with automation package)
  • Inner process box made of molybdenum, tungsten, graphite or CFC, especially recommended for debinding processes. The box is installed in the furnace with direct gas inlet and outlet and provides for better temperature uniformity. Generated exhaust gases will be directly lead out the inner process chamber during debinding. The change of gas inlet pathes after debinding results in a clean process gas atmosphere during sintering.

Additional equipment vacuum

  • Two-stage rotary vane pump with ball valve for pre-evacuating and heat-treating in a fine vacuum (up to 10-2 mbar) incl. electronic pressure sensor
  • Turbo molecular pump with slide valve for pre-evacuation and for heat treatment in a high vacuum (up to 10-5 mbar) including electronic pressure sensor and booster pump
  • Other vacuum pumps on request
  • Partial pressure operation: protective gas flushing at controlled underpressure (only with automation package)

Additional equipment cooling

  • Heat exchanger with closed-loop cooling water circuit
  • Direct cooling

Additional equipment for controls and documentation

  • Charge thermocouple with display
  • Temperature measurement at 2200  °C models with pyrometer in the upper temperature range and thermocouple, type C with automatic pull-out device for precise control results in the low temperature range (VHT 40/..-GR and larger)
  • Automation package with process control H3700
    • 12“ graphic touch panel
    • Input of all process data like temperatures, heating rates, gas injection, vacuum at the touch panel
    • Display of all process-relevant data on a process control diagram
    • Automatic gas supply for one process gas (N2, argon or non-flammable forming gas) with adjustable flow
    • Bypass for flooding and filling the chamber with process gas controlled by the program
    • Automatic pre- and post programs, including leak test for safe furnace operation
    • Automatic gas outlet with bellows valve and overflow valve (20 mbar relative) for over-pressure operation
    • Transducer for absolute and relative pressure
  • Process control and documentation via VCD software package or Nabertherm Control Center (NCC) for monitoring, documentation and control

Technical specifications

  VHT ../..-GR VHT ../..-MO VHT ../18-W VHT ../18-KE
Tmax 1800 °C, 2200 °C or 2400 °C 1200 °C or 1600 °C 1800 °C 1800 °C
Inert gas
Air/Oxygen - - -
Hydrogen 3,4 3 3 1,3
Rough vacuum and fine vacuum (>10-3 mbar) 2
High vacuum (<10-3 mbar) 4 2
Material of heater Graphite Molybdenum Tungsten MoSi2
Material of insulation Graphite felt Molybdenum Tungsten/Molybdenum Ceramic fiber
1Tmax reduces to 1400 °C ​​​​​​2Depending on the temperature
3Only with safety package for flammable gases 4Up to 1800 °C

 

Model Inner dimensions in mm Volume Max. charge Outer dimensions6 in mm Heating power in kW4
  w d h in l weight/kg W D H Graphite Molybdenum Tungsten Ceramic fiber
VHT 8/.. 170 240 200 8 5 1250 (800)1 1100 27005 27/27/-2 19/343 50 12
VHT 25/.. 250 400 250 25 20 1500 2500 2200 70/90/-2 45/653 85 25
VHT 40/.. 300 450 300 40 30 1600 26005 2300 83/103/1252 54/903 110 30
VHT 70/.. 375 500 375 70 50 18005 33005 2400 105/125/1502 70/1103 130 55
VHT 100/.. 450 550 450 100 75 1900 35005 2500 131/155/1752 90/1403 on request 85
VHT 250/.. 600 750 600 250 175 30001 4300 3100 180/210/-2 on request on request on request
VHT 500/.. 750 900 750 500 350 32001 4500 3300 220/260/-2 on request on request on request
1With separated switching system unit 21800 °C/2200 °C
31200 °C/1600 °C 4Depending on furnace design connected load might be higher 
5Dimensions may be smaller depending on the heater type 6External dimensions vary when furnace is equipped with additional equipment. Dimensions on request.

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Customer Test Center

What furnace is the right choice for this specific process? This question cannot always be answered easily. Therefore, we have set up our modern test center which is unique in respect to size and variety. A representative number of furnaces is available for tests for our customers.