Practices in isothermal forging for 258 mm-diameter titanium VT23 alloy hemisphere blanks

Abstract

The results of the backward isothermal extrusion process as to 258 mm-diameter titanium VT23 alloy hemisphere blank forgings having extended fitting adapters are presented. Using three blank sizes, the effect is studied of the two-junction isothermal forging parameters on the hemisphere blank forging qualities. The effect is shown of the strain extent and initial blank sizes at the first junction on the blank forging quality rating at the second junction. It is found that the required hemisphere blank forging qualities as to mechanical characteristics, macro- and microstructures, and geometries correspond to the initial 150 mm-diameter and 110 mm-high blanks being 35 % strained at the first junction. In so doing, the backward isothermal extrusion of the 258 mm-diameter hemisphere blank forgings increases an ultimate strength of 1079 up to 1270 MPa, an impact toughness of 20 up to 25 J/cm2 as well as decreases a blank forging of 11.5 up to 8.9 kg compared to standard similar hot die-forged blanks.