Ferrous parts are bonded together in a copper brazing furnace under suitable temperatures and a furnace atmosphere which, in the absence of parts, is comprised of at least 90% nitrogen, up to 7% combined hydrogen and carbon monoxide with hydrogen being greater than 50% of the total of CO and H.sub.2 and having a dew point between approximately -40.degree. to +10.degree. C. In the preheat section of a continuous belt furnace or the like, the dew point may range between -20.degree. to +10.degree. C. while in the furnace hot zone, the dew point is maintained between approximately -40.degree. to -10.degree. C. A brazing paste which is preferably a combined copper and 25-75% copper oxide paste is utilized. With such furnace atmosphere and paste composition, clean part surfaces, which permit superior wetting by molten copper and thus acceptable copper flow and penetration into the joint being bonded, are obtainable. The furnace atmospheres utilized enable increased life to be obtained from furnace materials such as brick insulation, muffles, conveyor belts, and heating elements.