Nozzle clogging is a common phenomenon in the continuous casting of steels, especially for aluminum killed steels, and has detrimental effects on the continuity of casting and the steel cleanliness. The formation and prevention of nozzle clogging during the continuous casting of steels was reviewed in the current study. The characterization of nozzle clogging was firstly summarized, finding that the composition, morphology, and structure of the nozzle clogging significantly depended on the steel grade, casting condition, and clogging degree. Then three factors affecting the formation of nozzle clogging was briefly summarized as the physical adhesion of high-melting-point inclusions, the temperature drop resulted from the insufficient preheating of nozzles and the temperature fluctuation of molten steel, and the chemical reactions occur during the continuous casting. The prevention methods of nozzle clogging could be roughly divided into 5 types, including the cleanliness improvement of steel, the liquid modification of inclusions, the fluid flow control inside the nozzle, the coating treatment on the inner surface of nozzles, and the external field treatment. Moreover, the challenge of the nozzle clogging control in the future was proposed. Multiple methods should be coordinated, especially the external field treatment should be developed to achieve a better inhibitory effect on the nozzle clogging.

The calcium treatment was the most popular and effective method to modify inclusions in the molten steel. For the modification of oxide inclusions, the partial liquid inclusion was suggested to avoid the nozzle clogging caused by solid inclusions, as well as the formation of hardly removed large liquid inclusions in the Al-killed Ca-treated steel. During the calcium treatment process, the added Ca firstly modified Al2O3 inclusions to liquid CaO-Al2O3 for T.CaT.O in steel. Meanwhile, the CaS/( CaO+Al2O3) in inclusions increased with a higher (T.Ca-T.O)/T.S ratio in steel. For the sulfide inclusion modification, the calcium treatment retarded the precipitation of linear sulfides along the grain boundary of the steel matrix and lower the deformability of CaS during the rolling process due to the higher hardness of CaS. The length of sulfides increased with a higher T.Ca content, while it decreased with lower T.O and T.S contents in steel. Influence factors of the calcium yield of the calcium treatment were summarized to steadily increase the calcium yield, including steel composition, temperature, feeding speed, etc. An empirical equation between the [Ca], T.Ca, T.O, T.S, and [Al] was fitted to predict the [Ca] content in steel. During solidification and cooling processes of Al-killed Ca-treated steels, inclusions transformed from liquid CaO-Al2O3-MgO in the molten steel to Al2O3-MgO-CaS in the solid steel due to the equilibrium change. Moreover, the focus on the calcium treatment in the future was proposed.

Microscopic self-propelled swimmers capable of autonomous navigation through complex environments provide appealing opportunities for localization, pick-up and delivery of micro and nanoscopic objects. Inspired by motile cells and bacteria, man-made microswimmers have been fabricated, and their motion in patterned surroundings has been experimentally studied. We propose to use self-driven artificial microswimmers for the separation of binary mixtures of colloids. We revealed different regimes of separation, including one with a velocity inversion. Our findings could be of use for various biological and medical applications.