METHOD FOR PRODUCING SEAMLESS LARGE-DIAMETER PIPES

摘要

The invention relates to metal-forming processing, namely to producing seamless steel pipes. The inventive method involves heating a solid cylindrical billet, applying a glass-based working lubricant on said billet and an extrusion tool, carrying out the billet piecing, extruding a pipe, separating the thus produced pipe from extrusion discard and releasing the pipe from the die. The piercing and pressing operations are carried out on a vertical hydraulic pipe-extrusion press at one operational cycle thereof. The billet piecing operation is carried out by means of a press mandrel in a container and is preceded by the billet prepressing. The pipe is extruded by a direct pressing method when a metal flows through a die downwards under the action of an extrusion stem provided with a pressing disc with an elongation ratio equal to or greater than 1.4. The working lubricant contains graphite taken in a graphite/glass volume ratio of (1:4)...(1:5). The invention makes it possible to combine the billet piercing and pipe extrusion operations, to simplify the structural design for the press and to reduce the size and the mass thereof, to improve the performance of the pipe pressing process and to reduce metal waste during piercing and extrusion.