Journal
MATERIALS & DESIGN
Volume 66, Issue -, Pages 258-266Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.matdes.2014.10.068
Keywords
Bainitic steel; Hot working; Constitutive modelling; Processing maps
Categories
Funding
- National High Technology Research and Development Program of China (863 Program) [2012AA03A504]
- Innovative Research Groups of the National Natural Science Foundation of China [51121061]
- Open Project Program of National Engineering Research Center for Equipment and Technology of Cold Strip Rolling [NECSR-201304]
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The hot deformation behaviour of low carbon bainitic steel, 29MnSiCrAlNiMo steel, was studied at a temperature range of 800-1100 degrees C and a strain rate range of 1 x 10 (2) to 1 x 10(1) s (1). The flow curves display two features, with steady-state region and without it. After a comprehensive consideration of the deformation temperature, strain rate and strain, a constitutive model was proposed, exhibiting a correlation coefficient of 0.982 between the experimental and predicted stress values. The result shows a decreased deformation activation energy from 460 to 267 kJ/mol with increasing strain level from 0.1 to 0.8. Processing maps at different strain levels were also constructed, which exhibit an expanded instability region with increasing strain. Microstructural observations show that the flow localisation occurred when the hot working was performed on the instability regions, and partial dynamic recrystallisation occurred along the grain boundaries and deformation bands, resulting in a mischcrystal structure. The optimum hot working processing parameters for the studied steel are at 930-980 degrees C and 0.001-0.014 s (1), and a full dynamic recrystallisation structure with a fine and homogeneous grain can be obtained. Microstructure observation verifies the applicability of the processing maps for optimising the processing parameters of the 29MnSiCrAlNiMo steel. (C) 2014 Elsevier Ltd. All rights reserved.
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