| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a dummy block with which the rolling of a skin layer of a billet into an extruded material is prevented without increasing the amount of refuse by pressing. Ž<P>SOLUTION: This block is a dummy block (10) which is arranged at the top of a stem for imparting pressing force to the billet which is charged in the container of an extruding device. An extrusion working surface (11) which domes into contact with the billet includes a projecting part (12) in the central part, the outside region of this projecting part (12) is made into an annular pocket part (20) and the projecting part (12) and the pocket part (20) are continuously formed through an inclined part (13) the cross-sectional area of which is made smaller toward the chip side of the projecting part (12). The inclined part (13) is inclined at the maximum inclined angle (θ1) of 25-60°to the reference surface (Q) which is passed through the deepest part of the pocket part (20) and crossed orthogonally to the extrusion axis (P) and the outer peripheral edge (16) of the pocket part (20) is parallel to the reference surface(Q) or formed by being pushed out forward the reference surface (Q). Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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