C8-STUDIU EXPERIMENTAL PRIVIND INFLUENȚAREGIMURILOR DE TRATAMENT TERMIC ASUPRAMICROSTRUCTURII ȘI TENACITĂȚII OȚELULUI C45
EXPERIMENTAL STUDY ON THE INFLUENCE OF HEAT
TREATMENT REGIMES ON THE MICROSTRUCTURE AND
TOUGHNESS OF C45 STEEL
The present paper investigates the correlation between the heat
treatment parameters (normalization, quenching in various media,
return), the microstructural evolution and the shock fracture behavior of
C45 grade carbon steel. The study involved the application of heating
cycles at 900oC, followed by cooling in water, oil and air, as well as
successive tempering at 220oC and 600oC. The experimental results
demonstrated a reduced penetration of the quenching of C45 steel into
oil, where a heterogeneous structure of troostite and martensite 43 HRC
was obtained, compared to the fully martensitic structure obtained in
water 58 HRC. The analysis of fibrosity and crystallity of the fracture
surfaces highlighted the transition from brittle cleavage rupture (specific
to the hardened state) to tenacious, fibrous rupture (specific to the
improvement state), reaching a maximum value of KCU resilience of 112
J/cm2 after high recovery. The paper validates the importance of
improvement treatment for machine parts.
Keywords: plain carbon steel, heat treatment, ductility, Rockwell
hardness.
Cuvinte cheie: Oțel carbon C45, tratament termic, ductilitate,
duritate Rockwell.