Research on an extrusion process with effective stick friction. 3rd Report. Forming of a thin-walled cylindrical tube.

A new concept of "tribo-extrusion" to produce a thin-walled tube is proposed. The forming process is similar to that for usual extrusion with mandrel, but a thinner tube wall can be formed utilizing the effective stick friction on the moving mandrel. The relative die pressure pD/Y predicted by an upper bound analysis for the tribo-extrusion was much lower than that for the usual extrusion within the reduction in area Re=9098% under the full stick friction condition. Using three kinds of work metal ring, the tribo-extrusion of a cylindrical thin-walled tube was investigated experimentally. The die pressure pD in the tribo-extrusion was much lower than that in the usual extrusion with Re≧90%. The pD in the tribo-extrusion of low carbon steel was about 2.12.5 GPa within Re=6098%, while it was impossible to finish the tube by the usual extrusion.