It is known that the flow characteristics of molten steel at the casting plays an important role in determining the quality of ingot, and there are some theoretical and experimental studies on the influence of the flow pattern and pouring velocity in top casting method. So far as the authors knows, there is no such systematic study on the pattern of the flow of molten steel in bottom casting pit, in which steel flows out of nozzle into the opening of runner bricks and then into mould.
This paper concerns the study of the flow patterns of molten steel in the bottom casting based on the theory of classical hydrodynamics as well as the results of some experimental measurements.
Considerations have been given to the relations between the variation of both openings of the inlet and the outlet side of the nozzles, and the distance of lifting the stopper and the flow pattern of molten steel.
In addition, the enlarging of the diameter of openings by the errosive action of flowing steel has been determined by measuring respectively in the case of rimming and killed steel in regard to the practical pouring data.
(1) In order to keep constant the pouring velocity the conditions of the enlarging of nozzle diameter was investigated, and was confirmed that the ideal condition could not be realized with fire clay refractories.
(2) The changing rate of flowing during the pouring of rimmed and killed steel due to the increase of the size of nozzle diameter by erosion was investigated, and was found that the former was by far more errosive than the latter, although both showed the same general trend.
(3) For the purpose of making possible to preestimate the effect of the rate of increase of nozzle diameter on the time of flowing steel the experimental data were formulated to a set of empirical formulas representing the correlation between the capacity of pouring ladle, rate of increase of nozzle diameter and the time of flow.
(4) The influence of the degree of nozzle opening on the control as well as the correlated pattern of flowing steel in regard to the dimension and relative position of nozzle and head was discussed and infered the approximate values.
(5) Assuming that the molten steel flowing from nozzle to mould at a pouring temperature higher than 1550° may be treated as an ordinary liquid, the flow was discussed with a result that it should be not laminar but turblent.
(6) The hydrodynamics of flowing molten steel passing through complicated path before casting was discussed in correlation to the trend of quality and surface appearance of ingots, and some basic principles for improving the flow pattern were postulated.
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