Apart from building hot zones for its new furnaces VAC AERO specializes in hot zone repair or replacement for all major brands of vacuum furnaces. Replacement hot zones are constructed using state of the art manufacturing technology and materials for years of reliable service. Both graphite-based and all-metal heat shield construction is available. All hot zone materials and new designs are fully tested in our own heat treating facilities before being offered to our customers. VAC AERO’s graphite-based hot zone designs continue to perform reliably under the most demanding thermal processing conditions. The insulation package for every VAC AERO hot zone is mounted on a stainless steel support ring. Whether it’s standard or custom hot zone rebuild for VAC AERO or any other major brand of vacuum furnace, our aftermarket specialists can provide you with a variety of replacement hot zones designed to meet your specific thermal processing applications!
As in any discipline, understanding the underlying scientific principles has profound practical implications when properly understood. In this series of articles we will review the first principles of vacuum technology and explain them using real world illustrations. Most industrial vacuum systems can, in broad based terms, be categorized in terms of low (i.e., “soft”), medium, high (i.e., “hard”) and ultra-high vacuum (Table 1). These ranges are very useful in describing the various pressure, flow, and other phenomenon encountered, which leads to a better understanding of vacuum pump selection and operation, and system operational requirements at the different vacuum levels. As shown by the difference in pressure from low to ultra-high vacuum, industrial vacuum systems must operate under an extremely wide range of pressure.
The word “eutectic” is one that I use in each of my brazing seminars during our discussions about brazing filler metals (BFMs) as well as metallurgical phase-diagrams, but it is also a word used in describing some of the features of metallurgical-structures within a solidified brazed joint. The word “eutectic” comes from the Greek word “eutektos” which means “easily melted”. Simply put, a eutectic-composition is an alloy of two or more metals, which, when heated to its melting point (solidus temp.), will completely change from solid to liquid at the same temperature (i.e., isothermally). Technically, theoreticians prefer to define a eutectic-reaction in reverse, proceeding from the molten state to the solid. However, I believe my description will help personnel in the brazing world grasp the general concept more easily.
After we have properly prepared our tool steel specimens, it is generally best to examine them as-polished before etching – unless we are simply doing a routine test, for depth of decarburization, degree of spheroidization, and so forth. Examination of selectively etched tool steel microstructures by light microscopy provides more information than standard etchants, such as nital, picral or Vilella’s reagent. Further, the images are more suitable for quantitative measurements, especially by image analysis. Specimens must be properly prepared, damage free, if selective etchants, or color etchants, are to be applied successfully. A number of etchants have been claimed to selectively etch certain carbides in tool steels. The response of these etchants has been evaluated using a variety of well-characterized tool steel compositions.
Booster pumps (aka Roots blowers or intermediate stage vacuum pumps) fall into the class of dry, gas transfer pumps. As a dry pump, they do not introduce oil or water into the pumped gas stream. Gas transfer is accomplished by mechanically means, that is the transfer of pumped gas molecules, rather than their collection, as with, foe example, cryogenic or turbomolecular pumps. The words “Roots blower” are synonymous with these pumps and the reason they are also commonly referred to as booster pumps is that they are mounted at the inlet of a primary/backing pump (such as a rotary vane, claw pump, or screw pump). They "boost" the performance of the primary pump improving pumpdown speed (much as a relay race in which the baton is passed from one runner to the next). The combination of Root blower and primary pump provides roughly a seven-fold increase in pumping speed and a ten-fold increase in pressure, in comparison to a primary pump alone.
Constructed of the finest materials and craftsmanship, VAC AERO’s high performance vacuum heat treating 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 and an 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.