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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

Compact horizontal vacuum furnace designs provide great flexibility, excellent performance and ease of operation for general heat treating and brazing applications to deliver value to commercial and in-house heat treaters alike.

CLICK HERE for Standard Furnace Sizes

vacuum-furnace-35The standard VAH Series Horizontal, Front-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.

CLICK HERE TO VIEW ACTUAL VACUUM FURNACE PRODUCTION SPECIFICATIONS

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.

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 from small laboratory units up to 54” wide x 54” high x 72” deep. Larger models 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 of up to 4000 lbs at 2400°F.

carbon_hot_zone.gifRadiation Shields: (Graphite-based Construction):

The standard graphite-based insulation package consists of three layers of carbon felt with an 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. A powered rotary clamping system is used to secure the bottom head during processing. All VAC AERO VAH Series furnaces come with a manually operated load dolly as standard equipment.

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 electro-pneumatic 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.

hardwarealarms_vah.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 VAH series Furnace Specifications

pdf_fileicon.gifDowload VAH series Auxiliary System Product Sheet

 
 

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VAC AERO News, Education & Training

vacuum-heat-treatVAC AERO’s Furnace Control System is Versatile and Operator-Friendly!

VAC VAC AERO’s uses the Honeywell HC900 process controller integrated with the Honeywell Experion HS software running on a Windows 7-based PC to provide Supervisory Control and Data Acquisition (SCADA). The Honeywell HC900 controller can connect remote users to the system, link multiple furnaces together, or to other operating systems in a facility. The VAC AERO control system is programmable, logic based and comprised of proven hardware components, suitably hardened for an "industrial shop" environment. The software has been optimised to cover all normal operating and alarm conditions. VAC AERO’s design philosophy is to simplify control by using the program capabilities to perform as many functions as possible, thereby reducing operator dependence. The software is optimised to control the machine functions and furnace temperature and to cover all normal operations, maintenance alerts and alarm conditions.

Vacuum Technology with "The Heat Treat Doctor"

dan-herring-615The Use of Molybdenum in Vacuum Furnace Applications

Vacuum furnace hot zones are manufactured using materials that can withstand temperatures in the range of 1315ºC (2400ºF) and higher. Of the various types of refractory metals in use, none is more common than molybdenum. The popularity and widespread use of molybdenum in vacuum furnaces is due to the wide range of properties that it exhibits, namely: high melting point, 2620ºC (4748ºF), low vapor pressure, high strength at elevated temperature, low thermal expansion, high thermal conductivity, high elastic modulus, high corrosion resistance and elevated recrystallization temperature, between 800º - 1200ºC (1470º - 2190ºF). Mechanical properties of molybdenum are influenced by purity, type and composition of any alloying elements and by microstructure. Properties such as strength, ductility, creep resistance and machinability are enhanced by additions of alloys such as titanium, zirconium, hafnium, carbon and potassium along with rare earth element (La, Y, Ce) oxides.

Vacuum Brazing with Dan Kay

dan-kay-615Removing Magnesium Buildup in Aluminum-brazing Vacuum Furnaces

As mentioned in a previous blog-article, magnesium (Mg), often referred to simply as “mag”, is a highly effective “getter” that is used when vacuum-brazing aluminum. Because Mg is very effective at gettering (reacting with and removing) both oxygen and moisture that may be present in a vacuum-furnace atmosphere during aluminum-brazing operations, it can effectively prevent (or minimize) the reaction of these elements with aluminum, thus allowing aluminum-brazing to occur. However, magnesium is a highly combustible metal, and when it condenses on the walls of a vacuum-furnace during aluminum brazing operations, extreme caution must be exercised in removing the condensed mag from the furnace walls during subsequent furnace clean-up, so that no sparks are generated which could cause rapid ignition of the condensed magnesium, resulting in explosive combustion, and even death. To prevent this, coating the walls of the vacuum furnace with a “non-stick” surface, such as shown in Fig. 1 may be highly effective.

Metallography with George Vander Voort

200-nital nlMetallographic Procedures for Cast Irons

Metallographic techniques for cast irons are similar to those for steels; with the exception that graphite retention is a more challenging task. Recommended procedures to prepare cast irons are given. Colloidal silica is an excellent final polishing abrasive for many metals and alloys. However, for pearlitic cast iron grades, colloidal silica often produces small etch spots on the specimen surface. In this case, OP-AN alumina suspension yields excellent results, much better than standard alumina abrasive powders made by the calcination process. Examples of cast iron structures revealed using a variety of etchants is presented.

Vacuum Pump Practice with Howard Tring

howard-tring-615Conductance and Throughput in Vacuum Pipelines

Let's talk a bit about conductance in vacuum system piping and why it has to be taken into consideration in the design of a typical vacuum furnace or similar vacuum system. Firstly though, we will discuss Throughput. Throughput - Have you ever wondered why vacuum pipes and connections are of several different sizes on any vacuum system? I would suggest that most users don’t really give it any thought. It is what it is. So let’s look at the sections of a vacuum system and again try to visualize those gas molecules, which are so tiny we can’t see them, and understand the conditions at different places in the system. Pumping speed of large mechanical vacuum pumps is usually indicated in cubic feet per minute. That can be denoted in several ways; cfm, cu ft /min or ft3 min-1. This is also shown in metric terms as cubic meters/hour, liters/min and l/min also shown as m3 hr-1 and l min-1.

Front and Bottom Loading Vacuum Furnaces

vacuum furnace-0115Constructed 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.

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