VAC AERO We’re excited to head down to Nashville for the Furnaces North America Conference and Expo. If you plan on attending the show, please be sure to stop by our booth number 418 to learn more about our latest vacuum furnaces, and most importantly... we're interested in learning about you, your business, and your needs. Our sales reps will be available to answer questions about how VAC AERO can help your business with exactly the vacuum processing solutions that you're looking for. See you there!
Furnaces North America is one of the largest Expos for manufacturers, commercial and captive heat treaters looking for the latest in technology, trends and training that can energize their productivity and profits. The FNA creates an exciting mix of education, technology, networking and exposition opportunities. Join the innovators and decision makers of the heat treating industry from around the world. You can’t afford to miss the FNA Conference and Expo! For more information please visit Furnaces North America 2014
Knowledge of vapor pressure and rates of evaporation of various materials is valuable information for those operating vacuum furnaces, whether we are heat treating or brazing at high temperature and low vacuum levels or dealing with outgassing at very low temperatures and pressures. When we think about a solid or liquid in a sealed vessel, we find that, even at room temperature and atmospheric pressure, there are molecules that leave the surface and go into the gaseous phase. The gas phase thus formed is called a vapor. The process of forming a vapor is known as evaporation and the rate of evaporation is determined by the temperature of the substance involved. In time, some of the evaporated molecules will, in all likelihood in the course of random movement, strike and stick to the surface of the vessel. This process is known as condensation and the rate of condensation is determined by the concentration of gas molecules (that is, the pressure of the evacuated gas). Eventually, the number of molecules leaving the surface of the substance is equal to the number returning to it (that is, the evaporation rate equals the condensation rate) and we have dynamic equilibrium. The (partial) pressure at which this occurs is known as the vapor pressure of the substance. Below this pressure, surface evaporation occurs faster than condensation, while above it, surface evaporation is slower.
A number of people have inquired about how to keep tubing or piping centered in holes or fittings prior to brazing, thinking (erroneously) that if the tubing/piping does not remain centered in the joint, but instead touches one surface or another inside the joint (due to lack of centering) that the joint therefore may be weakened thereby, or that the molten brazing filler metal (BFM) will not be able to penetrate the area where the tubing/piping contacts one of the surfaces inside the joint. That is incorrect thinking, because molten brazing filler metal (BFM) is able to penetrate extremely tight joints, even when there is metal-to-metal contact in some portions of the joint. The microscopic surface roughness of the mating surfaces inside the joint will allow the liquid BFM to penetrate completely. But, if you are in that group that feels that you must take steps to keep the tubing or piping centered in the joint to be brazed, and want to take steps to prevent any joint surfaces from touching, then there is a simple way by which to insure that the tubing/piping will remain centered in the joint throughout the braze-cycle.
Revealing the prior-austenite grain boundaries in heat treated steel is probably the most difficult, and frustrating task, faced by the metallographer or metallurgist. Grain boundaries, regardless of the type, are generally impossible to see in cast metals, as they solidify dendritically and segregation is present and often substantial. After deformation and annealing, if recrystallization occurs, grain boundaries in the product may be visible, but they are not necessarily prior-austenite grain boundaries. In a deformed, partially recrystallized specimen, it is usually possible to see both recrystallized and non-recrystallized grain boundaries. But, prior-austenite grain boundaries are those of the steel when it was austenitized prior to quenching and tempering. If the steel’s microstructure is fully martensitic after hardening, or contains some retained austenite or lower bainite, the prior-austenite grain boundaries may be revealed. They can often be revealed in specimens isothermally processed to obtain fully lower bainitic microstructures; but they cannot be revealed if the transformation microstructure consists of upper bainite, pearlite and/or ferrite. Composition also is important in trying to reveal the prior-austenite grain boundaries, as is the tempering temperature. In general, steels with low carbon contents and low phosphorous contents are very difficult subjects. This article summarizes the state-of-the-art in revealing prior-austenite grain boundaries.
This article completes the series of Five Main Reasons that vacuum is used in science and industry; To provide a working force, to remove active and reactive constituents, to remove trapped and dissolved gases, to decrease thermal transfer and finally to increase the mean free path to a useful dimension. The article printed back in January this year talked about solid, liquid and gas states of matter. The following is a short excerpt from that article. “In a gas the atoms and molecules are generally much further apart than in solids and liquids. In air at atmospheric pressure and room temperature the actual space occupied by atoms and molecules is about 0.01 per cent or one ten thousandth of the volume. The equivalent for solid copper is about 74 percent or close to three quarters. (So much for being called a “solid”). In air the molecules are in constant random movement, typically in a straight line, and the interatomic forces have little effect due to the space between the molecules. The moving molecules will constantly collide with other molecules and then move away in a different direction. These collisions occur about 10,000,000,000 times per second at atmospheric pressure”.
VAC 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.