Effect of hot deformation and austenitizing on the grain size of steels 4Kh4VMFSSh and 45Kh3V3MFSSh

Conclusions

• 1. In steel 4Kh4VMFSSh with an original grain size of grade 2–3 a homogeneous austenitic structure (grade 5.5–6) is formed under conditions of dynamic recrystallization after 15–50% deformation at 1100–1150°C. In steel 45Kh3V3MFSSh with an original grain size of grade 4–5 a homogeneous recrystallized structure with grain size of grade 7.5–8.5 is formed after 18–50% deformation at 1150–1200°C and also after 50% deformation at 1100°C. At other temperatures and deformations the austenite grain size either remains unchanged or it is refined, but not through the entire volume.

• 2. Phase recrystallization of steels 4Kh4VMFSSh and 45Kh3V3MFSSh cooled from deformation temperature in air is not accompanied by austenite grain refining if no recrystallization induced by mechanical cold working develops.

• 3. Austenitizing of deformed steels induces no essential changes in the structure even at the optimal temperature −1050°C for steel 4Kh4VMFSSh and 1100°C for steel 45Kh3V3MFSSh. If a completely homogeneous structure is not formed during deformation, it cannot be obtained during austenitizing.