Effects of N and B on continuous cooling transformation diagrams of Mo–V–Ti micro-alloyed steels |
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| Authors: | Wang Yuhui Liao Bo Liu Ligang Li Xianfeng Su Hang Yang Caifu |
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| Institution: | 1. National Key Laboratory of Metastable Materials Science &2. Technology , College of Material Science and Engineering, Yanshan University , Qinhuangdao 066004 , China;3. National Engineering Research Center for Equipment and Technology of Cold Strip Rolling , College of Mechanical Engineering, Yanshan University , Qinhuangdao 066004 , China;4. Technology , College of Material Science and Engineering, Yanshan University , Qinhuangdao 066004 , China;5. National Engineering Research Center for Equipment and Technology of Cold Strip Rolling , College of Mechanical Engineering, Yanshan University , Qinhuangdao 066004 , China;6. Division of Structural Material Research , Central Iron and Steel Research Institute , Beijing 100081 , China |
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| Abstract: | Effects of the single addition of nitrogen (N) and boron (B) and the combined addition of N and B on continuous cooling transformation (CCT) diagrams and properties of the three Mo–V–Ti micro-alloyed steels were investigated by means of a combined method of dilatometry and metallography. Microstructures observed in continuous cooled specimens were composed of pearlite (P), quasi-polygonal ferrite (QPF), granular bainite (GB), acicular ferrite (AF), lath-like bainite (LB) and martensite (M) depending on the cooling rates and transformation temperatures. Single addition of 12?ppm B effectively reduced the formation of QPF and broadened the cooling rate region for LB and M. Added N makes the action of B invalid and the QPF region was prominently broadened, and even though the cooling rate is higher than 50°C?s?1, it cannot obtain full bainite. |
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| Keywords: | CCT curves micro-alloyed steels microstructure pearlite polygonal ferrite acicular ferrite |
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