To provide a twist forward extruding method and a twist forward extruding apparatus by which extrusion at a low pressure is made possible by friction stirring and which is suitable to the production of a large size fine particle bulk material by which crystal grain is made finer at a breath by a single continuous process.
In this twist forward extruding method, after charging a billet B of a bar-like solid metal material into the charging hole of a cylindrical container 1 and when a die 2 and the billet B are relatively rotated around the extruding axis P of a pusher 3 while pressurizing the billet B with the pusher 3 toward a cylindrical die 2 which is arranged adjacently to the container 1, the pushing-in pressure of the pusher 3 and the rotational speed of the relative rotation are set to the thrusting pressure and the rotational speed so that plastic flow is generated on one end by generating frictional force and frictional heat between the one end of the billet B and the inside surface of the die hole by sliding them while bringing the one end of the billet B into contact with the inside surface of the die hole and the twist extrusion of the billet B is performed by imparting twisting shear strain while making the plastic flow continue to the side of the other end of the billet B.
MIZUNUMA SUSUMU
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