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Vacuum Furnace Systems, controls and Manufacturing
Vacuum Brazing and Vacuum Heat Treating Services
Thermal Spray Coating services, Plasma and High Velocity Oxy-fuel (HVOF) Spray Coatings and Inorganic Paint and Pack Coatings
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

vav_furnace-2.gifThe 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.

Custom or Standard Furnaces Sizes Available


STANDARD OPERATING TEMPERATURE RANGE: 1000°F - 2400°F (538°C - 1315°C)

TEMPERATURE UNIFORMITY: Meets or Exceeds AMS 2750 Requirements.


HOT ZONE:

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.

    FURNACE CHAMBER:

    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.

    VACUUM PUMPING SYSTEM:

    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.

    GAS QUENCH SYSTEM:

    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 COOLING SYSTEM:

    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.

    INSTALLATION AND START UP ASSISTANCE

    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.gifDowload VAV Series Furnace Specs

    pdf_fileicon.gifDowload VAV series Auxiliary System Product Sheet

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    VAC AERO News, Education & Training

    vacuum-furnace-manufacturersVAC AERO Ships Vacuum Furnace to Aerospace Manufacturer in Mexico!

    Burlington, August 18, 2014 - VAC AERO shipped a VAH 6660 HV-2 horizontal vacuum furnace to an international company’s plant in Mexico to process aerospace parts. This customer has a long history with VAC AERO, having purchased many vacuum furnaces for its plants all over the world over the last few decades. The furnace features an all-metal hot zone with a work chamber of 48” x 48” x 60” with a 4,000-pound load capacity. It utilizes gas cooling to 2-bar absolute pressure and operates at temperatures of 1,000 °F to 2,200 °F. The furnace is also equipped with a 35” diffusion pump and VAC AERO’s HC900 control system. A key control feature is the ability to independently control the work chamber zones for optimal work-load uniformity as well as the ability to program heat-treatment cycles that can then be run automatically and accurately allowing the operator to achieve the specific structure and properties required for their application. MORE INFO ON OUR VACUUM FURNACES

    Vacuum Technology with "The Heat Treat Doctor"

    vaccum-furnacesLow Temperature Heat Treatment

    Low temperature heat treatments that involve a vacuum purge at the onset of the cycle have become increasingly popular throughout the industry. These operations are conducted in vacuum furnaces and furnaces that employ a vacuum purge prior to the beginning of the heat process with parts placed inside a special vacuum tight vessel or in a retort. Processing being run using these methods take advantage of a highly controlled environment designed to minimize surface interactions. Low temperature vacuum heat treatment is used by both captive and commercial heat treaters and spans such diverse markets as Aerospace, Automotive, Electronics, Optics, Housewares, Industrial Products, Tool & Die, Military/Defense and Farm Implement to name a few. Most processes run in the temperatures range of 175°C – 730°C (350°F – 1350°F). Special applications extend these ranges down to as low as 120°C (250°F) and up to as high as 925°C (1700°F), but this is unusual.

    Vacuum Brazing with Dan Kay

    vaccum furnaceBraze Joint Design: “Percentage of Voids in a Joint can Increase with Overlap Distance".

    In my opinion, based on my experience, the amount of actual braze coverage in a joint is more important than the number of voids in that joint! As discussed in last month’s blog-article, a lap-joint with an overlap of “3T-to-6T” (where “T” is the thickness of the thinner of the two members being brazed) is all that is needed to provide full strength and hereticity in a properly designed brazed joint (1T-to-3T for aluminum alloys). By this I am saying that we need to look at the amount of GOOD braze coverage, rather than being overly concerned with trying to count the number of voids in a joint!  Counting voids is really the wrong way to approach the “goodness” of a brazed joint. Please note, that if someone brazed a lap-joint that used a 6T-overlap, and it contained about 50% void content (assuming the voids to be randomly distributed throughout the joint), that would still leave a net-overlap (after deducting all the areas of voids) of about 3T.

    Metallography with George Vander Voort

    vaccum furnacesMicrostructure of Ferrous Alloys

    The microstructure of iron-base alloys is very complicated and diverse, being influenced by chemical composition, material homogeneity, processing and section size. This article offers a brief explanation of the terminology describing the constituents in ferrous alloys, and offers a basic review of steel microstructures. Microstructures of castings look different from those of wrought products, even if they have the same chemical composition and are given the same heat treatment. In general, it is easiest to identify heat-treated structures after transformation and before tempering. For example, if a mixed microstructure of bainite and martensite is formed during quenching, these constituents will become more difficult to identify reliably as the tempering temperature used for the product increases toward the lower critical temperature. Further, ferrous metallographers tend to use nital almost exclusively for etching, but nital is not always the best reagent to use to properly reveal all microstructures.

    Vacuum Pump Practice with Howard Tring

    vaccum-furnaceOil Diffusion Pump Controls

    Oil diffusion pumps remain in popular use in the vacuum heat treating industry, possibly one of the few applications remaining for this type of high vacuum pump in the western world. The main reasons for their continued use are their longevity the lack of other options. When your process requires a pressure below that of a mechanical pump or mechanical pump and Roots pump combination a secondary vacuum pump has to be used. These are oil diffusion pumps, turbomolecular pumps and possibly cryogenic pumps. Turbomolecular pumps are limited in physical size due to the high rotor speeds needed to create molecular flow into the pump mechanism; and both “turbos” and “cryos” are very susceptible to process contamination. Large cryos are often used in vacuum coating applications but, as far as I am aware, not in vacuum heat treating applications.

    Front and Bottom Loading Vacuum Furnaces

    vacuum heat treating furnacesVAC AERO offers complete turnkey services, including planning, designing, building and installation of vacuum furnace systems and controls. VAC AERO’s experience, proven through decades of service in commercial heat treating, has provided us with valuable insight into the changing needs and rigorous demands of our furnace customers. As a result, VAC AERO has developed a keen understanding of the design and performance of vacuum furnace systems built to meet the most stringent requirements for reliability. VAC AERO’s vacuum furnace design innovations are thoroughly tested in our own heat treating facilities before being offered to our customers. That means better quality, reliability and efficiency to maximize uptime and productivity. Horizontal vacuum models provide great flexibility for general heat treating and brazing applications and Vertical bottom-loading models are ideal for processing large circular and/or long parts.

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