Effect of Final Cooling Temperature on Microstructure and Mechanical Properties of a Cr-Ni-Mo-V Bainite Steel

• Published in: Journal of materials engineering and performance Vol. 27; no. 9; pp. 4749 - 4759
• Main Authors: Zhang, Jian, Li, Chang-Sheng, Li, Bin-Zhou, Li, Zhen-Xing, Wang, Qi-Wen
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.09.2018
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Corrosion and Coatings; Engineering Design; Materials Science; Quality Control; Reliability; Safety and Risk; Tribology; thermomechanical control process; final cooling temperature; Cr-Ni-Mo-V steel; mechanical property; bainitic microstructure
• ISSN: 1059-9495; 1544-1024
• DOI: 10.1007/s11665-018-3288-8

The microstructural evolution and mechanical properties of a low-carbon high-strength bainitic steel under different final cooling temperatures were studied. The microstructures of the experimental steel at different final cooling temperatures were composed of acicular ferrite and granular bainite. A decrease in final cooling temperature resulted in an increase in volume fraction of granular bainite and a decrease in volume fraction of acicular ferrite. The specimen with the lowest final cooling temperature (459 °C) exhibited the highest yield strength, tensile strength, and yield ratio, and a lower total elongation than the specimens with the highest final cooling temperatures (501 and 535 °C) because of the higher volume fraction of granular bainite and finer bainitic ferrite lath. The specimen with the lowest final cooling temperature had a lower absorbed energy than that of the highest final cooling temperature, because the strip-like martensite–austenite (M-A) constituents that existed between the bainitic ferrite or in prior austenite grain boundaries reduced its toughness. At an intermediate final cooling temperature of 501 °C, the experimental steel exhibited excellent mechanical properties with a yield strength, tensile strength, and absorbed energy of 825 MPa, 1232 MPa, and 102 J, respectively.