Metal tubes are produced by extruding a hollow billet through an annular die opening defined by a die and a movable rod-shaped mandrel having a larger length than the tube to be produced, and by feeding the mandrel rod through the die together with the tube as it is being formed so that the tube as produced has the mandrel rod disposed therein along its entire length, whereby damage to the inner surface of the tube caused by scratching due to relative movement of the mandrel therewith is avoided and tubes having improved inner surface characteristics are obtained.
A process for the extrusion of tubes or similar hollow sections from a billet is disclosed within the billet is forced against a hollow extrusion die surrounding a mandrel and a mandrel support. A core passing through the extrusion billet moves in the direction of extrusion with the billet and is led through the mandrel into the space inside the resultant hollow section. The process of the present invention relieves the die of the high stresses which can otherwise lead to early failure of the die.
