Itt Corporation

Alfred Teves Gmbh

Arnold T Johnson

Glen A Gibbs

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. The seamless double-walled metal tube can be produced by instantaneously elevating the temperature of the surface of the steel employed in an unsealed double-walled metal tube to a brazing temperature while maintaining the tube material in a humidified gaseous atmosphere; maintaining the surface temperature of the steel tube for an interval sufficient to permit fusion between the metal capable of metallurgically bonding with the steel in the inner and the outer wall; after metal fusion has been achieved, allowing the resulting fused metal material to cool to a first lowered temperature 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 tube to a temperature below which the metal capable of metallurgical bonding is not reactive with oxygen.

Non-corrosive double-walled steel tube characterized in that the steel

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. The process including the steps of 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.

Sealed double wall steel tubing having steel outer surface

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.

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

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. The process including the steps of 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 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. This process can be employed successfully in manufacturing unique, double-wall tubing which is relatively flexible and highly corrosion resistant.

Partial elimination of copper plate from steel strip by mechanical means

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 which the brazing metal is not reactive with oxygen. This process can be employed successfully in manufacturing unique, seamless double-walled tubing which is relatively flexible and highly corrosion resistant.

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Davisburg, MI, United States of America

Arnold T Johnson