Machines high temperature

As there are a number of problems in the siting of the instruments, a variety of systems have been developed, each with its own advantages and disadvantages. By having the instrument attached directly to the machine, high temperatures and inaccessibility can be a problem, w hile the use of connecting pipes involves time delays and potential oxidation. 

Rockwell hardness testing has been extended to both low and high temperature regimes usually by enclosing the sample and part of the machine in an environmental chamber and using extensions for the anvil and indenter. 

Electrical Properties. Polysulfones offer excellent electrical insulative capabiUties and other electrical properties as can be seen from the data in Table 7. The resins exhibit low dielectric constants and dissipation factors even in the GH2 (microwave) frequency range. This performance is retained over a wide temperature range and has permitted appHcations such as printed wiring board substrates, electronic connectors, lighting sockets, business machine components, and automotive fuse housings, to name a few. The desirable electrical properties along with the inherent flame retardancy of polysulfones make these polymers prime candidates in many high temperature electrical and electronic appHcations. 

Depth-of-Gut Notching. Depth-of-cut notching (DOCN) is a localized wear process common when machining materials such as austenitic stainless steels or high temperature alloys. Notching is attributed to the chemical reaction of the tool material and the atmosphere, or to abrasion by the hard, sawtooth outer edge of the chip. DOCN may lead to tool fracture. 

A. T. Santhanam, G. P. Grab, G. A. Rolka, and P. Tierney, Proceedings of the Conference on High Temperature Productivity Machining—Materials and Processes, New Orleans, La., American Society for Metals, 1985, pp. 113—121. 

The resistance of graphite to thermal shock, its stabiUty at high temperatures, and its resistance to corrosion permit its use as self-supporting vessels to contain reactions at elevated temperatures (800—1700°C), eg, self-supporting reaction vessels for the direct chlorination of metal and alkaline-earth oxides. The vulnerabiUty of cemented joints in these appHcations requires close tolerance ( 0.10 mm) machining, a feat easily accompHshed on graphite with conventional metal machining equipment. 

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