Influence of on-line tempering parameters on microstructure of medium-carbon steel

Autor: Yan-xin Wu, Jian-xun Fu, Qijie Zhai, Xu Jie, Hua Zhang
Rok vydání: 2017
Předmět:
Zdroj: Journal of Iron and Steel Research International. 24:59-66
ISSN: 2210-3988
1006-706X
DOI: 10.1016/s1006-706x(17)30009-2
Popis: A new process involving ultra-fast cooling (UFC) and on-line tempering (OLT) was proposed to displace austempering process, which usually implements in a salt/lead bath and brings out serious pollution in the industrial application. The optimization of the new process, involving the evolution of the microstructure of medium-carbon steel during various cooling paths, was studied. The results show that the cooling path affected the final microstructure in terms of the fraction of pearlite, grain size and distribution of cementite in pearlite. Increasing the cooling rate or decreasing the OLT temperature contributes to restraining the transformation from austenite to ferrite, and simultaneously retains more austenite for the transformation of pearlite. It is also noted that bainite was observed in the microstructure at the cooling rate of 45 °C/s and the OLT temperature of 500 °C. Through either increasing the cooling rate or decreasing the OLT temperature, the distribution of cementite in pearlite is more dispersed and grain is refined. Taking the possibility of industrial applications into account, the optimal process of cooling at 45 °C/s followed by OLT at 600 °C after hot rolling was determined, which achieves a microstructure containing nearly full pearlite with an average grain size of approximately 7 μm and a homogeneously dispersed distribution of cementite in pearlite.
Databáze: OpenAIRE
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