Multistage Extrusion Research Articles

The Technology of Multistage Extrusion for Thin Walled Brass Cylinder

This paper analyzed the structure of the thin walled brass cylinder, calculated the deformation degree and extrusion ratio, and designed the multistage cold extrusion process. According to the cold extrusion process, the multistage extrusion mold structure and transfer device were designed. Compared with the stamping process, multistage cold extrusion process has high material utilization, high efficiency, small investment in equipment and other advantages of high strength, high precision and small surface roughness in parts production.

一方向貫通気孔を持つ多孔質アパタイトの製造と組織制御

By using molten wax colloidal process with graphite powders as combustible pore-forming agents, a method for controlling the porosity and pore size of porous hydroxapatite ceramics has been developed. Porous hydroxyapatite with unidirectionally aligned continuous pores were fabricated by multistage extrusion of green billets. Starting billet of this multistage extrusion was made from stacking hydoxyapatite green disks of outer diameter 50mm and inner diameter 25mm filled with 100% graphite green disks of 25mm. In order to make the porous matrix, the mixture of hyroxyapatite and graphite was used instead of hydroxyapatite. By the primary extrusion, hexagonal rods with the graphite in the central part were extruded. These extruded hexagonal rods were bundled to make composite billets for the next stage extrusion. This process was repeated for several stages. Finally, the extruded rods of proper stage were sintered. Size of the continuous pore can be controlled by total extrusion ratio. The pore diameter obtained in the present work was from 350μm to 8μm. The porosity can be controlled by the billet structure. The mean flexural strength of the porous hydroxyapatite ceramics obtained in this work was from 32MPa to 56MPa.

The western boundary of extrusion blocks in the southeastern Tibetan Plateau

The model about block extrusion related to collision between Eurasia and India which is proposed by Tapponnier et al. has not been accepted so far in the field. Based on kinematics and chronology, the Gailigong dextral strike-slip fault in west Yunnan and Nabang dextral strike-slip fault which is the part of Mogok belt are the western boundary of extrusion blocks, as the eastern boundary Red River-Ailaoshan left-lateral fault. And more studies show that as the important way for absorbing the convergence between two continents, the age of blocks multistage extrusion is about 23 and 13 Ma.

Development of upper bound technique for analysis of fracture in metal forming

An attempt is made to modify the plasticity theory for compressible materials and then to derive the upper bound theorem or the second extremum principle which incorporate normal velocity discontinuity; this discontinuity is considered to be a measure of fracture. The theorem is applied to predict the occurrence of fracture, central bursting in extrusion or drawing. The occurrence of fracture appears to depend on the value of the parameters in the theorem; these parameters may be related to ductility or workability of the material in question. The upper bound technique is then applied to multi-stage extrusion of a carbon steel for which the values of the parameters are given with some assumptions. It is thus shown that the stage at which central bursting occurs agrees with experimental results and that it apparently depends on the extrusion condition.