METHOD FOR EXTRUDING LARGE-DIAMETER TUBES Russian patent published in 2000 - IPC

FIELD: extrusion of large-diameter tubes. SUBSTANCE: method for extruding large-diameter tube with relation of wall thickness to diameter less than 0.1 comprises steps of placing plug in die holder; feeding heated ingot to container; pressing out ingot; piercing axial opening for forming sleeve; removing plug; separating bottom and extruding tube in gap between extrusion needle and wall of container during several transitions at predetermined basing of extrusion needles and piercing needle. In one case at changing cut-off and centering rings in die holder, by one stroke of punch extrusion is realized for several transitions. Annular bottom formed at each intermediate transition is separated. In other case when punch is shifted and next hollow extrusion needle is put on needle end protruding out of blank, extrusion is realized for several transitions. Then plug is removed and bottom of extruded tube is separated by means of needle having set of needles inserted one to another. EFFECT: possibility of providing extrusion tool loads not exceeding admissible values. 3 cl, 6 dwg