Studies on Vacuum Brazing (Report I) : Removing of oxide film from carbon steel surface and brazing alloy spreading mechanism(Welding Physics, Processes & Instruments)

概要

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Vacuum brazing of carbon steels was studied both on the removal of oxide film from carbon steels (S45C, S25C, Armco Fe) surface and brazing alloy (BAg-8b) spreading mechanism. This research was done in order to clarify the relation between the removing oxide film and decarborizing phenomenon, which occur by heating various oxidized carbon steels in vacuum. Moreover, the brazability was checked by spreading test on carbon steel surface, and oxidation, decarborizing and spreading phenomena were investigated. It was shown that, the decarborizing of carbon steel caused by heating in vacuum was promoted by the existence of oxide film on the specimen surface. This phenomenon for high carbon steel (S45C) was brought about more easily than for low carbon steel Armco Fe. Spreading is due to the primary diffusion of Cu of brazing alloy into grain boundary grooves formed on carbon steel surface by removal of oxide film during vacuum heating with carbon. Furthermore, it was determined that the activation energy for spreading of molten BAg-8b on polished surface is 44.2kCal/mol and 24kCal/mol on oxide surface of steel (S45C).