Study on Continuous Cooling and Isothermal Cooling Microstructure Transformation of High Strength Steel SCr440 for Automotive Fasteners and Application
李战卫, 于学森, 沈奎, et al. Study on Continuous Cooling and Isothermal Cooling Microstructure Transformation of High Strength Steel SCr440 for Automotive Fasteners and Application[J]. Special Steel, 2022, 43(2): 90-94.
李战卫, 于学森, 沈奎, et al. Study on Continuous Cooling and Isothermal Cooling Microstructure Transformation of High Strength Steel SCr440 for Automotive Fasteners and Application[J]. Special Steel, 2022, 43(2): 90-94.DOI:
The phase transformation characteristics of high strength steel SCr440 ( 0.40% C
1.00% Cr) for automotive fasteners are studied by thermal simulation. From 850 °C by cooling rate ≤ 1℃ /s continuous cooling
the transformed structure is ferrite and pearlite
and bainite and martensite occur in structure with cooling rate reached 2 ℃/s
by cooling rate ≥7 °C/s the main structure in steel is martensite and bainite. The pearlitic transformation temperature is 550 ~700 °C during isothermal conditions
and bainitic transformation occurs when the transformation temperature decreased below 550 °C. Based on thermal simulation results
the Φ 18 mm SCr440 steel rod has been successfully rolled
and can be used to manufacture 10.9 grade automobile flange bolts by cold drawing to Φ 17 mm rod
then spheroidizing annealing at 700 ~ 760 °C and cold drawing to Φ15.7 mm rod.