Effects of cooling after rolling and heat treatment on microstructures and mechanical properties of Mo-Ti microalloyed medium carbon steel

被引:10
作者
Li, Defa [1 ,3 ]
Dong, Hangyu [1 ,2 ]
Wu, Kaiming [1 ]
Isayev, Oleg [1 ]
Hress, Oleksandr [1 ]
Yershov, Serhii [1 ]
机构
[1] Wuhan Univ Sci & Technol, Int Res Inst Steel Technol, State Key Lab Refractories & Met, Hubei Prov Key Lab Syst Sci Met Proc, Wuhan 430081, Peoples R China
[2] Univ Texas El Paso, Lab Excellence Adv Steel Res, Mat Sci & Engn Program, Dept Met Mat & Biomed Engn, El Paso, TX 79968 USA
[3] Wuhan Iron & Steel Co Ltd, R&D Ctr, Baosteel Cent Res Inst, Wuhan Branch, Wuhan 430080, Hubei, Peoples R China
来源
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING | 2020年 / 773卷
基金
中国国家自然科学基金;
关键词
Heat treatment and cooling processes; Precipitation; Effective grain size; Martensitic lath; STRAIN-INDUCED PRECIPITATION; STRENGTHENING MECHANISMS; INTERPHASE PRECIPITATION; COILING TEMPERATURE; NB; AUSTENITE; MOLYBDENUM; MARTENSITE; EVOLUTION; BEHAVIOR;
D O I
10.1016/j.msea.2019.138808
中图分类号
TB3 [工程材料学];
学科分类号
0805 ; 080502 ;
摘要
The effects of four different processes, direct quenching + tempering (DQ + T), direct quenching + reheating and quenching + tempering (DQ + RQ + T), forced air cooling + reheating and quenching + tempering (AC + RQ + T), and furnace cooling + reheating and quenching + tempering (FC + RQ + T), on microstructures and precipitates of Mo-Ti microalloyed medium carbon steel were investigated by OM, SEM, TEM, EBSD and mechanical tests. The width of martensite laths (0.22 +/- 0.01 mu m) produced in DQ + RQ + T was similar to that generated in DQ + T and was narrower than those formed during AC + RQ + T and FC + RQ + T. The effective grain size of the DQ + RQ + T sample was found to be the smallest (0.98 +/- 0.38 mu m), thus it yielded the finest (Ti, Mo) C precipitates, manifested high strength and excellent plastic toughness, and generated uniform transverse and longitudinal properties. The strength of the DQ + RQ + T sample (longitudinal R-m = 1773 MPa) was slightly lower than that of the DQ + T samples and its elongation (A = 11.0%) and impact energy at -40 degrees C (A(kv) = 50 J/cm(2)) were greater than those of the other three samples. Before the RQ process, the DQ cooling process was employed in order to generate large angle grain boundaries to provide more nucleation sites for austenitization. Moreover, the DQ process inhibited the precipitation of Ti during cooling and then formed fine (Ti, Mo) C precipitates during reheating of RQ to prevent austenite grain growth. Therefore, the DQ + RQ + T process generated fully refined austenite grains, made the martensite structure and (Ti, Mo) C precipitates more uniform, and enhanced the effects of fine grain strengthening and precipitation strengthening. In addition, the plasticity and the toughness of the fine and uniform equiaxed grains were also significantly improved, and the formation of acicular cementites was impeded.
引用
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页数:11
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