| The Monthly Newsletter of VAC AERO International Inc. | If you are having trouble viewing this e-mail, click here. To log on to the VAC AERO web site, please click here. |
April 2010 |
905-827-4171 |
| Hot Zone Construction | by Dan Herring | This is the eighth in a series of articles in our Vacuum Heat-Treatment Series. This part talks about vacuum hot zones, their history, construction and maintenance. The type of hot zone construction is often important both to the material and to the process.
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The first commercial vacuum furnace was sold to industry in 1929. In these early years vacuum furnaces were hot-wall retort designs; that is, alloy retorts placed inside atmosphere furnaces in which a vacuum was pulled on the retort interior. By the late 1950s, vacuum furnaces were gaining wider acceptance, particularly within the commercial heat-treatment industry. Larger sizes were especially in demand, prompting furnace manufacturers to consider alternative designs. The early 1960s saw the introduction of the first all-graphite-felt hot zone with graphite (cloth) heating elements. This was followed a few years later by a hot zone construction consisting of a molybdenum hot face backed with Kaowool insulation and graphite (tubular) heating elements. Read more >> |
Part nine of this series discusses the types of heating systems available for vacuum furnaces and explains how temperature uniformity is achieved in various styles of furnaces.
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| Thermocouples in Furnace Brazing - Part One | by Dan Kay | Proper temperature control within each furnace brazing cycle is essential. It will not only insure proper brazing filler metal (BFM) flow, but can also prevent part distortion. To accomplish this, multiple thermocouples (or "TC's" as they are often called) need to be placed in strategic positions within each furnace load.
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In this first of two articles on TC's and their use in brazing, I'd like to briefly look at what TC's are, and the types commonly available for use in brazing furnaces today (much more exhaustive discussions about TC's can be found on the websites of a number of thermocouple manufacturers and suppliers). In next month's article, I'll describe the actual use and placement of these TC's in different brazing furnace cycles. A thermocouple (not "thermal-couple") is a temperature measuring device that consists of two metal wires, called thermoelements, each of a different composition, and joined together at one end to form a measuring junction (MJ), "couple", or "hot junction". Read more >> |
NEXT TIME - We will look at correct placement of TC's in furnace brazing loads, and how, together with correct furnace heating/cooling rates, they can help to maximize uniformity of temperature throughout each brazing load and minimize any distortion of components that are being brazed together.
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| Understanding Copper & Copper Alloy Heat Treatment | ||
| By Daniel H. Herring | ||
Different combinations of properties can be produced by varying the heat treatment of copper and its alloys-influencing strength, hardness, ductility, conductivity, impact resistance, and inelasticity.
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Common heat treatments applied to copper and its alloys are: 1) Homogenizing to reduce chemical segregation and coring of cast structures, and create a more uniform structure in hot worked materials. 2) Annealing to soften work hardened (strain-hardened) materials. 3) Stress relief to stabilize properties and improve strength and dimensions particularly for cold worked parts, and to reduce residual stress. 4) Solution treating and precipitation (age) hardening to provide increased strength by precipitation of constituents from solid solution. 5) Quenching hardening by a martensitic-like transformation followed by tempering. |
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