Process for gas carburising

摘要

The invention relates to a process for carburising metallic workpieces in a furnace under high temperatures and in an atmosphere containing CO and H2, in which the atmosphere is formed on the basis of an oxygen-containing hydrocarbon medium fed to the furnace, in particular methanol, and on the basis of nitrogen, an enrichment medium being additionally introduced to set a certain carbon level. To achieve a carburising atmosphere having an initially high carbon conversion number, it is proposed that in at least some of the said initial phase carbon dioxide or oxygen or an oxygen/air mixture and - in correlation thereto - an increased amount of enrichment medium is fed to the furnace and on the other hand the N2 feed is correspondingly simultaneously decreased, while in the later process phase, in which the carbon diffusion becomes decisive for the carburization, the carbon dioxide feed or oxygen feed and the increased feed of enrichment medium is shut off again with switching on of the nitrogen feed.