On the basis of previous research on a physical model and analytical estimates, a new injector design is pro posed. Industrial tests of the new design are conducted on the continuous slab casting machine at Alchevsk metallur gical works. The new design includes a ring covering the dosing nozzle. The gas is injected through calibrated holes in special refractory tubes. The tests indicate that a refining effect is obtained at gas flow rates of 10-12 L/min.
A new annular injection block containing pores of the optimum size has been developed. Use of the block maximizes the removal of nonmetallic inclusions from the tundish bath. The efficiency of the block has been confirmed by theoretical calculations, data obtained from physical modeling, and factory tests.The metallurgical practice of using injection equipment in tundishes has shown that, under certain conditions, such injection reduces the number of nonmetallic inclusions in the molten steel if the injection process is carried out in a certain regime [1 -3]. The mechanism by which steel is refined by injecting it with argon involves the capture of nonmetallic inclusions by argon bubbles and transport of the inclusions to the layer of slag [4,5].At the same time, data reported in [6 -8] indicates that the practice of injecting inert gas into a tundish requires strict control over the size of the bubbles and the rate at which they are formed. Such control is necessary because a high gas flow rate leads to emulsification of the slag and exposure of the surface of the metal, which in turn facilitates the metal's secondary oxidation. It has been determined that the homogenizing effect of the injection process is diminished as the distance between the location of the injection block and the metering nozzle increases.Inert gas is fed into the tundish through injection equipment located in the bottom of the tundish. The main shortcomings of the equipment which is presently used for this purpose: the low degree of efficiency with which nonmetallic inclusions are removed from the steel due to the use of injection blocks having pores of different diameters; the fact that only the volumes of metal in the tundish which are located just above the injection unit can be injected; a high gas flow rate, which results in emulsification of the slag and lowers the temperature of the metal being cast [9 -11].The goal of our investigation was to create a porous refractory block that maximizes the removal of nonmetallic inclusions, stabilizes gas permeability over its entire service life (several dozen hours), and allows real-time correction of gas flow rate during the injection process.The data in [12] indicates that the total number of inclusions entrained each second by gas bubbles formed by an injection system will be:where H is the height of the metal bath, m; V st is the volume of the liquid steel displaced by a bubble during its flotation to the free surface, m 3 ; T 0 and T ¥ are the temperatures of the gas at the inlet and inside the tundish, respectively,°C; Q g is the rate of flow of the gas, m 3 ·sec -1 ; d b is the size of a bubble, m; r i is the density of an inclusion, kg·m -3 . Then the percentage of nonmetallic inclusions removed from the steel d, %, can be represented aswhere t is the time of injection, sec. Data calculated with Eqs. (1) and (2) shows that inclusions are most efficiently removed from steel when the diam-
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