Microstructure Properties of Steel After Quenching and Partitioning in Bainite Zone
ZHU Shuai1, KANG Yong-lin1, KUANG Shuang2, JIANG Ying-hua2
1. School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China 2. Shougang Research Institute of Technology, Beijing 100043, China
Abstract：Quenching and partitioning process depends on an optimum quenching temperature and a partitioning temperature between martensite start temperature and martensite finish temperature to avoid bainite transformation during partitioning stage, the highest austenite volume fraction can be obtained under this condition and constrained carbon equilibrium (CCE) model. However, retained austenite fraction obtained by practical experiments is no more than 8%, which limited plasticity improvement. Partitioning in bainite zone (Q&PB) after quenching from austenite was proposed and used on (0.21-0.29)C-(1.5-2.0)Si-(1.5-2.1)Mn steel, 25% elongation and 12.3% retained austenite volume fraction was gotten using Q&PB process with tensile strength of 1 000-1 100 MPa, the highest product of strength and ductility was 36.6 GPa·%. The results of quenching temperature and partitioning temperature tests show that: the strength is little effected by temperature, elongation and product of strength and ductility are increased with partitioning temperature, and the increasing rate of 270 ℃ quenching sample is higher than that of 245 ℃ quenching sample. An excellent combination of strength and elongation is realized using novel Q&PB process, which can provide a new idea for the development of new generation steel.
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2014, Vol. 49 
