Transient Behavior and Thermodynamics of Inclusions in Al-Ti-Deoxidized and Ca-Treated Steel
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TITANIUM is widely used as a significant alloying element, which can effectively increase steel production quality. As a common stabilizing element injected into molten steel, titanium tends to bind the soluble carbon and nitrogen and to form carbides, nitrides, and carbonitrides.[1–3] Titanium has been proven to generate some dispersion of titanium oxides, which can improve the nucleation ratio of intragranular bainite during the hot rolling process.[4–6] Intragranular bainite is beneficial for improving the mechanical properties around the welded region of the steel. Moreover, it is suggested that fine Ti-oxides also promote acicular ferrite formation and grain refinement in C-Mn-Cr steel, hence improving TONGSHENG ZHANG is with the School of Metallurgy and Environment, Central South University, No. 932 South Lushan Road, Changsha 410083, P.R. China and also with the National Center for International Research of Clean Metallurgy, Central South University, Changsha, P.R. China. YANDONG LI is with the College of Mechanical and Electrical Engineering, Yangtze Normal University, Chongqing 408000, P.R. China. Contact e-mail: [email protected] CHENGJUN LIU and MAOFA JIANG are with the School of Metallurg, Northeastern University, No. 11 Wenhua Road, Shenyang 110819, P.R. China. Manuscript submitted January 18, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
steel strength and toughness.[7,8] However, TiOx inclusions easily agglomerate and form clusters to deteriorate the mechanical property of the final steel products; they also clog the submerged entry nozzle (SEN) to lower production efficiency during the continuous casting process.[8–10] During the past decades, intensive research on nonmetallic inclusions in Al-Ti complex deoxidized steel have been carried out.[9–25] Wang et al.[13] studied the effect of Al and Ti contents on the dynamic evolution of inclusions in Ti-bearing Al-deoxidized melt at 1873 K and found that the inclusions in the high-Al and high-Ti melt are easy to aggregate, which leads to a loose structure, unlike alumina inclusion. Basu et al.[14] and Kawashima et al.[15] reported that Ti-bearing Al-killed steels have a strong tendency to reoxidation by air or molten slag, and the Al-Ti-O system complex inclusions generated during the reoxidation process can worsen the castability. However, the equilibrium phases of the Al-Ti-O system in molten steel are still in dispute. Theoretically, it is currently difficult to get the liquid inclusions in Ti-bearing steel through inclusion control within the Al-Ti-O system. Calcium treatment can effectively modify alumina or spinel inclusions to liquid calcium aluminate inclusion in steelworks, which is advantageous not only for the mechanical properties of final steel production, but also for the manufacturing process, such as reducing the nozzle clogging possibility in continuous casting,
particularly in the Al-killed steel production process.[26–28] A number of research studies have been conducted and focused on the size distribution, thermodynamic calculati
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