In an extrusion process comprising the steps of fabricating a metal billet, heating said billet for a predetermined time and at a selected temperature to increase its plasticity and then forcing said heated billet through a small orifice to produce a desired extruded object, the improvement comprising the steps of randomly inserting a plurality of small metallic thermal tabs at different cross sectional depths in said billet as a part of said fabricating step, and examining said extruded object at each thermal tab location for determining the crystal structure at each extruded thermal tab thus revealing the maximum temperature reached during extrusion in each respective tab location section of the extruded object, whereby the thermal profile of said extruded object during extrusion may be determined.
A method of extruding a plurality of billets. The method includes (a) preheating a billet to a preheat temperature; (b) extruding the billet so that the exit temperature of the extrusion is within a predetermined temperature range; (c) measuring the extrusion pressure during (b); (d) comparing the measured extrusion pressure to a reference pressure range; (e) if the extrusion pressure was below said reference pressure range, resetting the preheat temperature so that it is lowered by a predetermined increment; (f) if the extrusion pressure climbed above the reference pressure range, resetting the preheat temperature so that it is raised by a predetermined increment; (g) preheating another billet to the preheat temperature; and (h) repeating (b)-(g) until all the billets have been extruded. In a preferred embodiment, the billet is formed form an aluminum alloy.
