A three-dimensional mathematical model of gasliquid two-phase flow has been established to study the flow behavior of liquid steel in the tundish. The effect of the argon flow rate and casting speed on the flow behavior of liquid steel, as well as the migration behavior of argon bubbles, was investigated. The results from the mathematical model were found to be consistent with those from the tundish water model. There were some swirl flows around the stopper when the annular argon blowing process was adopted; the flow of liquid steel near the liquid surface was active around the stopper. With increased argon flow rate, the vortex range and intensity around the stopper gradually increased, and the vertical flow velocity of the liquid steel in the vicinity of the stopper increased; the argon volume flow in the tundish and mold all increased. With increased casting speed, the vortex range and intensity around the stopper gradually decreased, the peak value of vertical flow velocity of liquid steel at the vicinity of the stopper decreased, and the distribution and ratio of argon volume flow between the tundish and the mold decreased. To avoid slag entrapment and purify the liquid steel, the argon flow rate should not be more than 3 L·min−1. These results provide a theoretical basis to optimize the parameters of the annular argon blowing at the upper nozzle and improve the slab quality.

A series of novel 1,3,4-thiadiazole derivatives of glucosides were synthesized by the starting materials d-glucose and 5-amino-1,3,4-thiadiazole-2-thiol in good yields with employing a convergent synthetic route. The results of bioactivities showed that some of the target compounds exhibited good antifungal activities. Especially, compounds 4i showed higher bioactivities against Phytophthora infestans (P. infestans), with the EC50 values of 3.43, than that of Dimethomorph (5.52 μg/ml). In addition, the target compounds exhibited moderate to poor antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas campestris pv. citri (Xcc).

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The bubbles generated by argon blowing in a nozzle have important effects on the flow and heat transfer behavior of mold slag. To determine the effect of argon blowing on the flow and heat transfer behavior of liquid slag in the mold, we developed three-dimensional mathematical models coupled the volume of fluid and discrete phase models. The results showed a small circulation flow of liquid mold slag occurred near the nozzle side face and the mold narrow face respectively at the center plane between the mold wide faces. Additionally, we identified a larger circulation of liquid mold slag in the middle region of the mold. With increased argon flow rate, the flow velocity peak at the liquid steel and slag interface decreased, the temperature of the liquid mold slag increased. A moderate flow rate of argon improved the uniformity of flow velocity and temperature distribution of liquid slag and reduced the flow velocity peak at the interface of the liquid steel and slag. To avoid the solidification of liquid steel at the steel-slag interface near the mold face, moderately high casting speed and argon flow rate and larger inclination angle and immersion depth of the submerged entry nozzle may be beneficial. These results provide a theoretical basis to optimize the parameters of the argon blowing process and improve slab quality.

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