Non-corrosive double walled tube and process for making the same

Details Non-corrosive double walled tube and process for making the same Non-corrosive double walled tube and process for making the same

1991-01-25

1993-06-29

Heinrich, Samuel M.

Metal fusion bonding

Process

With shaping

228227, 228254, 138142, 138171, B23K 119

Patent

active

052226522

ABSTRACT:
A seamless double-walled tube having high corrosion resistance and relative flexibility prepared by a process for brazing non-ferritic steel surfaces such as nickel chromium or stainless steel to which a suitable brazing alloy such as copper has been mechanically attache which includes the steps of instantaneously elevating the surface of the stainless steel to a brazing temperature while maintaining the material in a humidified gaseous atmosphere consisting essentially of a non-reactive carrier gas and a reactive gas present in sufficient concentrations to achieve fluxing; maintaining the surface temperature of the steel for an interval sufficient to permit fusion between the selected metal and the non-ferritic steel surface; after metal fusion has been achieved, allowing the resulting fused metal material to cool to a first lowered temperature in a controlled non-oxidative atmosphere at a rate which retards the formation of fine-grained steel crystals in the metal; and after reaching a metallurgical transformation point, rapidly cooling the fused metal in a controlled atmosphere to a temperature below which the brazing metal is not reactive with oxygen.

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