VAC Burlington, Ontario, February 16, 2015 - VAC AERO has recently received orders for three complete all-metal hot zone refurbishments for customers in Florida, Connecticut and Indiana, in the Aerospace, Medical and Commercial Heat Treatment industry sectors. The retrofit work is for two horizontal and one vertical furnace. VAC AERO hot zones feature unitized construction for easy removal and maintenance. The lightweight design’s low thermal mass enables faster quenching and longer life. The heat shield package consists of one layer of .020” thick lanthanted molybdenum (Mola) sheet backed by one layer of .010” thick molybdenum sheet, and three layers of .014” stainless steel sheet.
We continue our discussion on the many factors that must go into the decision making process during the acquisition phase of a vacuum furnace. Part One focused on how one goes about choosing the right furnace for the job and talked about the various choices for hot zones (e.g. insulation, heating elements, etc.). We now continue this discussion by looking at other common vacuum furnace features and options. Recall that the four common elements of any vacuum furnace are: Hot zone (c.f. Part One), Heating elements (c.f. Part One), Pumps and controls. Once decisions have been made in these areas, other ancillary items (e.g. partial pressure control, loaders, etc.) must also be considered and will be talked about here as well.
A number of brazing shops today combine brazing and heat-treatment in their vacuum furnaces to join components together and then obtain certain desired base-metal properties in those brazed components via rapid cooling (quenching) immediately after brazing is done, and before the components are removed from the furnace. Thus, the same vacuum-furnace brazing cycle combines brazing and heat-treatment, yielding clean brazed components with special base-metal properties to meet unique end-use service conditions. Vacuum furnaces today offer a number of options regarding the introduction and use of circulating gases in the furnace hot-zone during brazing processes.
The reflected light microscope is the most commonly used tool for the study of the microstructure of metals. It has long been recognized that the microstructure of metals and alloys has a profound influence on many of their properties. Mechanical properties (strength, toughness, ductility, etc.) are influenced much more than physical properties (many are insensitive to microstructure). The structure of metals and alloys can be viewed at a wide range of levels - macrostructure, microstructure, and ultra-microstructure. Microstructural examination should always begin with the light microscope progressing from low magnifications to higher magnifications, followed by the use of electron instruments, as needed.
Even as turbomolecular vacuum pumps have displaced most small laboratory sized oil diffusion pumps these days because of perceived ease of use and cleanliness, most high vacuum heat treating furnaces still rely on a large oil diffusion pumps to generate the pressures below about 10-3 Torr needed for many metal conditioning processes. The main reason for this is that turbomolecular vacuum pumps have a physical size limit due to the high rotational speed of the rotor. That size limit is around 320 mm or 13 inches inlet diameter and may vary a small amount from manufacturer to manufacturer. In many cases the pumping speed may not be high enough as it is directly related to the inlet size of the pump.
Constructed 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.