Microstructure transformation of SCM415H steel for high strength automotive fasteners

doi:10.13251/j.issn.0254-6051.2025.01.010

Abstract

Abstract: The phase transformation characteristics of the SCM415H steel for automotive fasteners were studied by thermal simulation. The cooling rate of 0.25 ℃/s produces a microstructure of ferrite and pearlite, while the bainite and martensite occurs with the cooling rate reaches 0.5 ℃/s. The cooling rate of 5 ℃/s results in a microstructure of mainly martensite and bainite, and that of 15 ℃/s or above results in a microstructure of mainly martensite. The pearlitic transformation temperature is 700-575 ℃ during isothermal conditions. The nose tip temperature is about 660 ℃, and completion time of the phase transformation is about 428 s. Based on the tested results, the steel wires with a diameter of 24 mm were successfully produced, and then grade 10.9 automobile fasteners were successfully produced after one spheroidizing annealing and two drawing processes.

Key words: steel for automotive fasteners, SCM415H, continuous cooling, isothermal transformation, spheroidite grade

CLC Number:

TG142.1

Chu Feng, Li Zhanwei, Yu Xuesen, Zhang Jiming. Microstructure transformation of SCM415H steel for high strength automotive fasteners[J]. Heat Treatment of Metals, 2025, 50(1): 63-67.

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