Anomalous grain growth in 42KhMFA steel

Conclusions

• 1. The basic reason for anomalous grain growth in 42KhMFA steel in heating to 900–1000°C is not the melting method but the solidification conditions promoting the occurrence of macro- and microchemical inhomogeneities causing nonuniformity in second-phase particle distribution.

• 2. Different production methods of melting, forging, and rolling with small degrees of deformation do not change the tendency of 42KhMFA steel to mixed grain size in heating to 900–1000°C.

• 3. The greatest degree of mixed grain size is observed in heating case 42KhMFA-ÉSR steel (retarded cooling of the ingot) to 960°C but it is almost completely absent with the same heating of samples from an ingot rapidly cooled in solidification.

• 4. Forging with a large degree of reduction and subsequent annealing eliminates the tendency toward the occurrence of mixed grain size in 42KhMFA steel in heating to 900–1000° C regardless of the method of melting it as a result of the more uniform distribution of second-phase barrier particles on the grain boundaries.

• 5. The formation of ruptures in the austenitic grain boundaries and the dispersion of the brain boundaries in heating probably occur as a result of the appearance of annealing twins in areas free of barrier particles (carbonitrides, oxides, etc.).