Method for producing multi-walled metallic tubes

Abstract

A method for producing a tube ( 10 ) from metal, which consists of an inner tube ( 5 ) and at least one outer tube ( 7 ) surrounding the same, is provided. To create the outer tube ( 7 ), a metal strip ( 2 ) running in longitudinally is formed around the inner tube ( 5 ) moved in its axial direction so as to form a slit tube in such a way that its edges running in the longitudinal direction lie against one another at a slit extending in the longitudinal direction. The slit is welded to complete an outer tube that is closed all around. The inner tube ( 5 ) is cooled and the the finished outer tube ( 7 ) is reduced in its diameter until it is in contact with the cooled inner tube ( 5 ) in at least one reducing stage.

1 . Method for producing a tube ( 10 ) from metal, which consists of an inner tube ( 5 ) and at least one outer tube ( 7 ) surrounding the same, wherein:
 to create the outer tube ( 7 ), a metal strip ( 2 ) running in longitudinally is formed around the inner tube ( 5 ) moved in its axial direction so as to form a slit tube in such a way that its edges running in the longitudinal direction lie against one another at a slit extending in the longitudinal direction,   the slit is welded to complete an outer tube that is closed all around, characterized   in that the inner tube ( 5 ) is cooled and   in that the finished outer tube ( 7 ) is reduced in its diameter until it is in contact with the cooled inner tube ( 5 ) in at least one reducing stage.   
     
     
         2 . Method according to  claim 1 , characterized in that the inner surface of the outer tube ( 7 ) and/or the outer surface of the inner tube ( 5 ) is/are cleaned and/or activated chemically or with plasma before the reducing stage. 
     
     
         3 . Method according to  claim 1 , characterized in that the outer tube ( 7 ) is heated before the reducing stage. 
     
     
         4 . Method according to one of the preceding claims, characterized in that the inner tube ( 5 ) and the metal strip ( 2 ) consist of identical metals. 
     
     
         5 . Method according to  claim 4 , characterized in that the inner tube ( 5 ) and the metal strip ( 2 ) consist of steel, high-grade steel or a nonferrous metal. 
     
     
         6 . Method according to one of  claims 1  to  3 , characterized in that the inner tube ( 5 ) and the metal strip ( 2 ) consist of different metals. 
     
     
         7 . Method according to  claim 6 , characterized in that the inner tube ( 5 ) consists of aluminum and the metal strip ( 2 ) consists of copper. 
     
     
         8 . Method according to one of the preceding claims, characterized in that the method also comprises the drawing down of the metal tube ( 10 ), which has a specific initial diameter, to a final diameter that is reduced in comparison with the initial diameter. 
     
     
         9 . Method according to  claim 8 , characterized in that, in the drawing down of the metal tube ( 10 ), the wail thicknesses of the inner tube ( 5 ) and of the outer tube ( 7 ) are reduced. 
     
     
         10 . Method according to one of the preceding claims, characterized in that the inner tube ( 5 ) is a double-walled or multi-walled tube. 
     
     
         11 . Method according to one of the preceding claims, characterized in that the method also comprises the recrystallization annealing of the metal tube ( 10 ). 
     
     
         12 . Method according to one of  claims 1 - 10 , characterized in that an adhesive is applied to the inner surface of the outer tube ( 7 ) and/or the outer surface of the inner tube ( 5 ) before the reducing stage. 
     
     
         13 . Method according to one of the preceding claims, characterized in that the inner tube ( 5 ) comprises a cable core or contains a filling of some other kind.