Change in the structure and phase composition of steel 15Kh1M1FL with prolonged aging

Conclusions

• 1. The amount and composition of carbide phase in steel 15Kh1M1FL after prolonged aging depends greatly on the original heat treatment, which should produce even decomposition of the α solid solution after tempering. The heat treatment conditions must be such that the structure of the steel contains no retained austenite after normalization.

• 2. Reducing the cooling rate during normalization to a rate resulting in the eutectoid transformation produces uneven distribution of carbide particles after aging and substantially impairs the dispersity of the carbide phase.

• 3. Heating in the critical temperature range during normalization and during tempering induces the formation of a large number of unevenly distributed large clusters of carbides.

• 4. Raising the normalization temperature increases the dispersity of the carbide particles and makes their distribution more even. The dispersity of the carbide phase can be improved by raising the normalization temperature 100–120°C above Ac₃.