Effect of quenched and tempered treatment

normalizing & quenched and tempered treatment on micro¬structure and properties of 42CrMo forging crankshaft steel is studied by means of metallographic microscope observation and mechanical performance analysis. The results show that after the quenching and tempering treatment ( 860 ℃ quenched + 580℃ tempered)

the base structure for the forging crankshaft billet is temped sorbite and much amount of white ferrite with coarse grain non-homogeneously distributed at the central area of crankshaft. Its mechanical properties are TS 997 ~ 1211 MPa

YS 990 〜1204 MPa

el. 11% ~ 13%

RA 40% -48%

and impact energy 72 ~92 J. On the contrary

with a normalizing pretreatment(880℃ air cooling) before the quenching and tempering treatment process

the microstructure for the 42CrMo forging crankshaft steel become more uniform

its mechanical properties are TS 1100 〜1220 MPa

YS 1107 ~ 1188 MPa

el. 13% ~ 15%

RA 50% ~56% and impact energy 83 ~91 J. Therefore

the normalizing pretreatment at 880 °C air quenching at 860 °C and high temperature tempering treatment at 580 T is the optimized heat treatment process for the 42CrMo forging crankshaft steel.