Abstract
In tube extrusion, a billet of larger diameter than the tube diameter is generally used, and in this case an extrusion machine of larger capacity is required and the extruded tubes are subjected to relatively large thickness deviation. As a method overcoming these disadvantages, the Raflo Process to extrude large tubes by using smaller billets has been proposed, but details have not been reported. The author has carried out a basic study of this process. This paper is concerned with the disc extrusion as the first stage deformation in the Raflo Process.
Billets of pure lead, 30 mm in diameter and 100 mm in length were used. Disc extrusion was carried out to a thickness t0, 1 or 2 mm, in which the extrusion force and the limiting diameter for disc spread, Dmax, were measured. Both the die inlet profile radius, r, and the plate angle, θ, at the center were varied.
A minimum extrusion force was observed at r=1 mm for both t0=1 and 2 mm. The largest values of Dmax are 60 mm for t0=1 mm and 100 mm for t0=2 mm. Although there is little effect of θ on Dmax, the extrusion force shows maximum value at θ=0° for both t0=1 and 2 mm. Regarding thickness variation in extruded discs, the disc thickness decreases with the distance from the center regardless of r. Thus, the limit of diameter for each required disc thickness have been evaluated.
