1. The ductility of steel 9KhF in cast and forged states over the interval of 750–1230°C depends on the austenite grain size. The coarser the grain, the lower is the steel plasticity and the more susceptible it is to cracking in the process of deformation at temperatures close to the lower range of forging temperatures (750–900°C). 2. The resistance of steel 9KhG to deformation also depends on the size of the austenite grain. The highest resistance to deformation is to be registered when the average size of the grain is 0.4 mm. The minimum resistance to deformation is manifested by steel with the grain size of 0.2 mm (in case and forged states). 3. A coarse-grained austenite structure appears after prolonged heating prior to forging over the 1230–1260°C range (furnace temperature). In the case of high reduction this structure may be refined, but the austenite grains remain still inadmissibly large unless the central zone is duly forged out. 4. The flaws of metallurgical origin may be partially welded up if the reduction is sufficiently high, and in case of an intensive axial flow of metal in the central zone they may be squeezed out into refuse. If the squeeze is low, deformation affects mainly the peripheral layers and the defects of the central zone shift from the end to the center of the forging with respect to its surface. 5. The surface cracks appearing in the process of forging do not only prevent the use of high pressure, but make it necessary to provide for excessive machining allowances. This lowers the average degree of deformation along the cross-section. Hence, the greater is the number of cracks appearingin the forging process (i.e., the less ductile is the metal), the less affected is the central zone of the casting by forging, and the greater becomes the chance for internal cracks to appear in consequence of heat treatment.