TUBE EXTRUSION METHOD Russian patent published in 1997 - IPC

FIELD: tube production in horizontal presses. SUBSTANCE: method comprises steps of heating initial blank, piercing axial opening in it, working blank, secondarily heating it and extruding tube through gap between die and mandrel. At piercing diameter of axial opening of tube is less than inner diameter of extruded tube. Cylindrical protrusion with tapered transition step from blank body is formed on front end of tubular blank; diameter of of said protrusion is more than outer diameter of tube. Then blank is worked and said cylindrical protrusion is turned to cone with diameter of its end being less than outer diameter of tube. Axial opening is turned in such a way that along its length corresponding to length of end protrusion diameter of said opening is less than inner diameter of tube by 1 - 5%. Remaining portion of said opening has diameter more than inner diameter of tube. At next extrusion stage mandrel is used; said mandrel has back end curvilinearily expanded until diameter more than inner diameter of tube. Before extrusion mandrel is introduced to axial opening of blank until joining lateral surface of its leading end with surface of axial opening of blank protrusion and engaging lateral curvilinear surface of rear end of mandrel with rib of axial opening of blank. Then end protrusion of blank is placed along extrusion axis in die hole and back end of mandrel together with pressure pad is centered along axis of container. EFFECT: lowered difference thickness of walls of extruded tubes and reduced number of their surface flaws. 2 dwg