B - Operations – Transporting – 23 – K
Patent
B - Operations, Transporting
23
K
48/47, 113/83
B23K 1/008 (2006.01) B23K 35/30 (2006.01) B23K 35/38 (2006.01)
Patent
CA 1163869
IMPROVED BRAZING PROCESS ABSTRACT OF THE DISCLOSURE 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 H2 and having a dew point between approximately -40 to + 10°C. In the preheat section of a continuous belt furnace or the like, the dew point may range between -20 to +10°C while in the furnace hot zone, the dew point is maintained between approximately -40 to -10°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 insula- tion, muffles, conveyor belts, and heating elements. BACKGROUND OF THE INVENTION The present invention relates to copper brazing and more particularly to the copper brazing of ferrous parts under particular furnace atmospheres which enable improved bonding and increases furnace material life. Copper brazing is a commonly utilized technique for joining ferrous parts with close fitting joints (less than 0.1 mm wide gaps). Typically, such ferrous parts may comprise carbon steel, alloy steel and stainless steel and by melting a
348066
Airco Inc.
Gowling Lafleur Henderson Llp
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