Carburization resistance of austenitic stainless steel tubes
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United States of America Patent
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Apr 12, 1983
Grant Date -
N/A
app pub date -
Nov 21, 1980
filing date -
Nov 21, 1980
priority date (Note) -
Expired
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Abstract
Protection of cast austenitic stainless steel tubes is provided against initiation of carburization by (a) cold-working the inner surfaces of said tubes to deform the surface to such a degree that upon the subsequent heat treatment of step (b) below, dissolution of the M.sub.23 C.sub.6 carbides in the deformed region is accompanied by recrystallization resulting in a refined micrograin structure in the deformed regions to a substantially uniform minimum depth of about 20 microns; and (b) heating the cold-worked inner surfaces of said tubes, for an effective amount of time, at a temperature between its recrystallization temperature and its melting temperature, in an atmosphere of which the oxygen partial pressure is at least oxidizing with respect to chromium.
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