Abstract: A seamless double-walled metal tube which has an outer wall composed of steel having a face-centered cubic grain structure, an inner wall concentrically disposed within the outer wall, the inner wall composed of a steel having a face-centered cubic grain structure, the inner wall having an outerwardly oriented surface directed toward an inwardly oriented surface of the outer wall. The seamless double-wall metal tube also has an intermediate bonding metal region interposed between and metallurgically bonded to the inner wall and the outer wall. The intermediate bonding region is composed of a metal capable of metallurgically bonding with the inner wall and the outer wall.

Abstract: A non-corrosive double-wall tubing in which an unbrazed, unsealed continuous double-wall tube of a given circumference is formed from a metal sheet composed of a first non-ferritic metal having a first defined region of exposed non-ferritic metal and a second region of a second metal in overlying relationship thereto, said exposed region having a width essentially equal to the circumference of the finished tube.

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 transfo

Abstract: A process for producing non-corrosive double-wall tubing in which an unbrazed, unsealed continuous double-wall tube of a given circumference is formed from a metal sheet composed of a first non-ferritic metal having a first defined region of exposed non-ferritic metal and a second region of a second metal in overlying relationship thereto, said exposed region having a width essentially equal to the circumference of the finished tube.

Abstract: 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 attached 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 wh