Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1987-03-12
1989-04-11
Roy, Upendra
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
148 115N, 148 131, 148128, 219534, 219535, 219549, H05B 306, B23K 102
Patent
active
048203599
ABSTRACT:
A process for thermally stress-relieving a stressed portion of a metallic tube is disclosed herein. The process generally comprises the steps of inserting a small diameter radiant heater into the open end of the metallic conduit and then positioning it adjacent to the portion to be stress relieved, and heating this portion to a temperature between about 1150.degree. F. to 1500.degree. F. for a time period of between about four and twelve minutes, depending upon wall thickness. In order to determine the proper amount of electrical power to apply to the radiant heater, the emissivity of the stressed portion of the conduit is first measured by heating a portion of the section to incandescence at a known power level, and then determining the temperature of the incandescent tube by means of a pyrometer which compares the intensity of two selected colors or wavelengths of the transmitted light. This process is particularly useful in thermally stress-relieving the U-bends of heat exchanger tubes formed from Inconel.RTM. 600 that are used in nuclear steam engines. It may also be used to stress-relieve such heat exchanger tubes in regions where the reinforcing sleeves have been welded into their interiors. Such thermal stress relieving renders the tubes less susceptible to intragranular stress corrosion cracking.
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EPRI Document No. NP-2629LD "Evaluation of Steam Generator U-Bend Tubes from the Trojan Nuclear Power Plant" Sep., 1982, by Aspden and Kurchirka.
EPRI Document No. NP-3056 "In Situ Heat Treatment and Polythionic Testing of Inconel 600 Row One Steam Generator U-Bends," Apr., 1983, by Gilkison.
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Bevilacqua Bruce W.
Burack Robert D.
Cheng Wenche W.
Gilkison Joseph M.
Pement Fredric W.
Roy Upendra
Westinghouse Electric Corp.
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