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Vacuum Furnace Technology column by Dan Herring, Metallography column by George Vander Voort, Vacuum Brazing column by Dan Kay, Vacuum Pump column by Howard Tring and other Educational Resources

Vertical vacuum furnaces combine fast cycle times and quenching speeds to provide better uniformity of large production parts with complex geometries and are ideal for processing large circular parts such as rings, stators or engine casings and long parts like shafts or rolls.

CLICK HERE  for Standard Furnaces Sizes

vacuum-furnace-v350The standard VAV Series Vertical, Bottom-loading, Vacuum Heat Treating and Brazing Furnace can be customized to suit unique applications such as high pressure gas quenching, high temperature heat treating, ultra-clean processing and more.

The furnace is designed to have fast heating rates to very uniform temperatures at high vacuum levels. Standard units are equipped with a gas quench system capable of cooling the load rapidly from processing temperatures at quench pressures up to two bar.

Advanced microprocessor controls are used exclusively to ensure precise control and repeatability. VAC AERO control systems can be integrated with internal networks and offer extensive data collection capabilities. VAC AERO also manufactures auxiliary equipment for quench gas storage and furnace cooling requirements.


VAC AERO Vacuum Gas Quench Furnace features and capabilities include:

  • Operating temperatures up to 2400°F (1315°C).
  • Ultimate vacuum levels in the 10-6 torr range.
  • Modular hot zone design for easy maintenance.
  • All-metal hot zones are available for ultra-high vacuum processing.
  • Alternatively, economical graphite-based insulation provides extended durability.
  • Heating elements available in lightweight curved graphite or molybdenum strip.
  • Selectable gas quench pressures from 2 bar to 10 bar.
  • Fully automated control systems including PC-based controls with remote access.
  • Optional convection heating capability.


TEMPERATURE UNIFORMITY: Meets or Exceeds AMS 2750 Requirements.


VAC AERO hot zones have unitized construction for easy removal and maintenance. Lightweight design with low thermal mass and inertia for faster quenching and long life.

  • Work Load Size: Standard sizes up to 84” diameter x 84" high. Larger models are also available.
  • Heating Elements: Customer’s choice of lightweight curved graphite, pure or lanthanated molybdenum strip.
  • Hearth: Constructed with quickly removable hearth rails of pure molybdenum designed to support uniformly distributed loads up to 4000 lbs at 2400°F.

    vert_hot_zone-3.gifRadiation Shields: (Graphite-based Construction):

    The standard graphite-based insulation package consists of three layers of carbon felt with a inner facing of graphite foil bonded carbon composite for added protection and enhanced reflectivity. The heat shield package is supported by a stainless steel assembly that also acts as a manifold to distribute the quenching gas uniformly throughout the workload.

    Radiation Shields (All-Metal Construction):

    For ultra-clean processing applications, VAC AERO also offers an all-metal hot zone construction. The standard all-metal insulation package consists of two layers of pure molybdenum sheet backed by three layers of stainless steel sheet. The heat shield package is supported by a stainless steel assembly that also acts as a manifold to distribute the quenching gas uniformly throughout the workload.


    The chamber and heads are a double-wall water-cooled design, primed and painted the customer's choice of colour. The chamber is equipped with all necessary thermocouple jacks, gauge ports, pumping ports and gas quench entries conveniently located for easy access. The tank assembly is vertically aligned with a bottom opening load head. The bottom head and the load are raised and lowered smoothly by a constant speed, ball screw driven lifting jack. Once lowered, the bottom head rolls out from beneath the furnace by means of a powered drive assembly to allow 360° access to the load. The tank is equipped with a powered rotary clamping system to secure the bottom head during processing. A "ground fault" system is used to detect if the load or fixtures touch the heating elements during loading or unloading and will stop the elevator to prevent damage.


    The vacuum pumpdown is automatic and interlocked. The VAC AERO design uses a holding pump to maintain a low pressure on the diffusion pump foreline at all times. This feature, combined with proper timed sequencing of vacuum valves, virtually eliminates backstreaming of pump oils.

    • Mechanical Pump: Roughing Pump and Booster combination appropriately sized for furnace volume.
    • Diffusion Pump: Varian series complete with charge of Dow Corning fluid.
    • Holding Pump: Rotary vane pump.
    • Main, Roughing and Foreline Valves: Right angle poppet valve with electropneumatic operation.
    • Partial Pressure Capabilities: The furnace can be operated at partial pressures up to 1 torr (1000 microns) of inert gas (argon or nitrogen, whichever is used for quenching). Failsafe hydrogen partial pressure systems are also available.


    VAC AERO’s IG Series Quench Gas Storage Systems are available as an option.

    External recirculating inert gas quenching system distributes quench gas through circumferentially located internal nozzles for rapid, uniform cooling of the work load. The system includes:

    • Quench blower powered by electric motor with soft start.
    • Special high efficiency tube/fin heat exchanger.
    • Complete quench piping.
    • Selectable operating pressure.

    vertical_hardwarealarms.gifPROCESS CONTROLS with SCADA:

    The VAC AERO control system is programmable and logic based. The design philosophy of VAC AERO is to simplify control by using the program capabilities to perform as many functions as possible, thereby reducing operator dependence. VAC AERO has also chosen proven hardware components, suitably hardened for an "industrial shop" environment. The system uses a state-of-the-art Hybrid controller to control the machine functions and furnace temperature. The controller integrates with software running on a personal computer to provide Supervisory Control and Data Acquisition (SCADA). Operator interface is provided though an LCD touch-screen mounted in a control panel. An extensive range of standard displays is available.

    The key benefits of this system are:

    • Compatible with plant wide SCADA and network integration.
    • Process cycle validation.
    • Extensive alarm and event management and reporting.
    • Temperature control using advanced algorithms, auto tuning, and multiple PID loops.
    • Operator sign-on/sign-off security provides up to 255 control levels to limit operator control of individual items of plant and equipment.
    • Enhanced maintenance and troubleshooting management and trending.

    Vacuum Instrumentation: A Vacuum Gauge Controller with 2 station, thermocouple gauge and 1 station Penning (cold cathode) gauge is used to monitor the chamber and the pumping system. This instrument is integrated with the process controller to provide dedicated setpoints that control all critical vacuum-related process functions.

    Overtemperature Safety Controller: Digital manual set 0°F - 3100°F, Type S.

    Power Supply: The heating element power is supplied by an A.C. water cooled power supply containing single phase VRT assemblies. Each VRT has a 0 – 100% trim control for optimum temperature uniformity in the hot zone.


    Furnace water system consists of a compact manifold containing all necessary pressure regulators, valves, pressure switches and flow regulators with supply and drain hoses and fittings. As an option, VAC AERO can provide a Dual Loop Cooling System to supply coolant to the furnace.


    The system is shipped complete, tested and ready for installation. VAC AERO offers installation supervision or complete installation services. After installation, a qualified VAC AERO technician will visit the site to commission the equipment and provide instruction in furnace operation. As part of every furnace contract, VAC AERO also provides pre-delivery training in heat treating processes furnace operation and maintenance.

    pdf_fileicon.gifDownload VAV Series Furnace Specs

    pdf_fileicon.gifDownload VAV series Auxiliary System Product Sheet


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    VAC AERO News, Education & Training

    vacuum-pump-seriesVAC AERO Launches a New Vacuum Pump Technology Column with Dan Herring in collaboration with Edwards Vacuum!

    Burlington, Ontario, August 17, 2015 - A new column, written by vacuum heat treating expert Dan Herring “The Heat Treat Doctor”® in collaboration with Edwards Vacuum will be published monthly and offer helpful tips and techniques on vacuum pumping systems to a worldwide audience of individuals using all types of vacuum equipment. The first article will appear in the September 15th “What’s Hot!”. This Vac-Aero exclusive publication launched back in September 2007 and contains hundreds of archived articles can now be found in the “Resources” section of the VAC AERO website where anyone can sign up for the monthly newsletter. Keeping pace with the development of new vacuum processing technologies is the reason VAC AERO takes pride in its continued support of the metal treating community by helping to promote, collaborate and assist others in their search for solutions on important issues in the practice and application of vacuum processing.

    Vacuum Technology with "The Heat Treat Doctor"

    joint-ni-p-interlayer nlVacuum Diffusion Bonding

    Many of us who use vacuum furnaces are all too familiar with and have learned how to counteract the unintentional diffusion bonding that has been known to occur between component parts exposed to high temperatures and low vacuum levels. By contrast, vacuum technology that has found an important niche is that of diffusion bonding by design2-6. Vacuum diffusion bonding relies on temperature, pressure, time, and (ultra low) vacuum levels to facilitate atomic exchange across the interface between the materials. The process will work on similar or dissimilar materials so long as they are in intimate contact with one another. Vacuum diffusion bonding can be performed with or without pressure being applied and with or without the assistance of a short-lived low melting point “filler metal” (i.e. “activation layers or interlayer”) to facilitate the joining process.

    Vacuum Brazing with Dan Kay

    Table-2 nl303 stainless steel -- Is it a good choice for brazing?

    303 stainless steel is a machinable grade of 304-stainless steel. As mentioned in my earlier article (about 321-stainless), austenitic stainless steels are essentially iron-based alloys with at least 10.5% (or more) chromium added to it, as well as from 8-12% nickel, have inherent corrosion resistance, are usually very brazeable, are generally non-magnetic, and do not require (or effectively respond to) subsequent heat-treatment after brazing. They are primarily used in the “annealed” (soft) condition in end-use service. 303-Stainless - This machinable version of 304-stainless is generally available in either of two chemistries, standard 303, or 303Se. The use of 303Se has apparently decreased significantly over the years, but it is still available. The standard grade of 303 contains a minimum of 0.15-percent sulfur added to its chemistry, the sulfur being added for machinability purposes.

    Metallography with George Vander Voort

    Figure-2-nlWhat is a Normal, Uni-Modal Grain Size Distribution?

    ASTM Test Method E 112 says it covers test methods to determine the average grain size of specimens with a uni-modal distribution of grain areas, diameters or intercept lengths. It says that these distributions are approximately log-normal. But, it does not describe how one can determine if their specimen’s grain size distribution is a uni-modal normal (Gaussian) distribution. ASTM E 1181, Standard Test Methods for Characterizing Duplex Grain Sizes, says it covers test methods to characterize grain size in products with any other distribution (other than a “single log-normal distribution of grain sizes”). But, the only example given in Appendix X2 shows the percentage of the number of intercept measurements in 38 length classes from 0 to 1 to 37 to 38 mm. Thirty eight classes is far too many to properly reveal the grain size distribution. This procedure reveals a log-normal distribution but it is not in terms of ASTM grain size numbers, which makes it less useful.

    Vacuum Pump Practice with Dan Herring

    pirani nlProper Selection and Use of Vacuum Gauges – Part One

    Selecting the correct vacuum gauge or gauges is critical to the success of a heat treatment process. It is important to know how they work and what options are available so that the correct choice can be made. There are several important considerations when using a vacuum gauge. They include the method of operation, the gas composition (inert or reactive, corrosive), the gas sensitivity (calibration factor), and the process being performed in your system. Given the wide range of pressures encountered when running processes in vacuum furnaces (a staggering 9 orders of magnitude), no one gauge is adequate over the entire range of possible vacuum levels. As with vacuum pumps, multiple gauges are necessary to properly cover the entire operating range with the needed precision and accuracy. Given that it is critical to monitor the vacuum pressure at various points in the process and perhaps multiple locations throughout the vacuum system, the correct selection of each gauge ensures that we achieve optimal results.

    Front and Bottom Loading Vacuum Furnaces

    vacuum-furnace-3448Constructed of the finest materials and craftsmanship, VAC AERO’s high performance vacuum furnaces are operator friendly and designed to minimize maintenance and downtime to deliver outstanding quality and  value to commercial and in-house heat treaters alike. VAC AERO’s vacuum furnaces are designed for rapid heating rates to very uniform temperatures at high vacuum levels and can be customized to suit unique applications such as high pressure gas quenching, high temperature heat treating, ultra-clean processing and more. VAC AERO’s high efficiency hot zones are designed for easy maintenance and reduced energy consumption. Our external quench system allows for easy maintenance of the heat exchanger and quench motor. A high efficiency blower and motor combine fast cycle times and quenching speeds to provide uniform gas distribution and superior cooling performance from processing temperatures at pressures of up to 10 bar.