Based on the aforementioned finding in ODS steels, the recrystallization processing was extensively stud­ied to change the substantially elongated grain struc­ture to the equi-axed grain structure. The Y2O3 content should be <0.25 mass % to attain the recrys­tallized structure in the ODS ferritic steels. The two types of 12Cr-ODS steels in the chemical composi­tion of 0.23Y2O3-2W-0.4Ti (A3) and 0.34Y2O3-3W- 0.4Ti (A15) were extruded at 1150 °C, followed by 60% cold rolling and annealed at 1200 °C for 1 h. From these heat-treated bars, the internal creep rup­ture specimens were machined and tested at 650 °C. Figure 1835 exhibits a comparison of the creep rupture strength of recrystallized (A3) and unrecrys — tallized (A15) 12Cr-ODS steels at 650 °C, where
von Mises’ equivalent stress was estimated for the internal hoop stress. The unrecrystallized specimen shows significant strength anisotropy in uni-axial and internal creep rupture strength, whereas the recrystal­lized specimens reveal decrease of anisotropy, where uni-axial creep rupture strength decreases and inter­nal strength approaches the uni-axial strength. These results demonstrate that the recrystallization process adequately improves the creep rupture strength in the internal hoop direction. Furthermore, softening by recrystallization makes it possible to manufacture cladding by cold-rolling processing.