A Study for Production of Bimetal Rods and Powder-Packed Metal Tubes

点击翻译按钮获取中文摘要

Three subjects were studied;(1) effects of relative strength (Y_A/Y_B) and relative size of core (r_A/r_B) and extrusion ratio (R) on the workability of bimetal rods with hard core (A) and soft sleeve (B) (2) effect of working method on the workability of powder-packed metal tubes and (3) numerical analysis for deformation of bimetal rods during extrusion.(1) Workability of bimetal rods: The experiments were carried out using Al alloys and copper as core material and aluminum and lead as sleeve (Y_A/Y_B=3-12), ranging from .3 to .9 of R_A/r_B. (a) The effect of R was not remarkable if R>1.5, but in the range of R>1.5 the decrease of R was of advantage to proportional (sound) extrusion of the rod with small r_A/r_B. (b) The proportional extrusion was more easily done for medium value of r_A/r_B than for small of large value. (c) The fracture mode for small value of r_A/r_B was periodic necking of core and that for large value was cracking of sleeve.(2) Workability of powder-packed metal tubes: Three types of metal working, namely, hydrostatic extrusion, swaging and roller dies drawing were done on 6 mm Ag tube (1mm thickness) filled by alumina powder (<.3 m dia.). The proportional forming was carried out in hydrostatic extrusion and swaging, but cracking of sleeve was occasionally observed in roller dies drawing, which will be attributed to change of the sectional shape of tube to ellipse.(3) Numerical analysis: Under some assumptions the strain distribution of core along the longitudinal direction was estimated by the variation method, which should give the minimum deformation energy for a given extrusion increment. The shape of core in extruded rod was determined by the strain distribution. The results of simulation has good agreement with experimental result.