Basis for the electromagnetic throttling of steel

Electromagnetic throttling is an alternative to present methods of flow control for continuous casting of steel. This paper presents the underlying theory of electromagnetic throttling or, more specifically, the "pinch effect." The effect of conductivity, frequency, and pouring-tube diameter on the magnitude of electromagnetically induced force is discussed. The induced forces affect stream flow, which can be explained, in part, by Bernoulli\´s equation. A factor is developed to provide a calculation of counterpressure that retards stream flow. The theoretical stream loss, which constitutes a large portion of the total loss, is determined as a function of ferrostatic head pressure. Experimental electromagnetic throttling results are presented with mercury using a frequency of 244 kHz, without a refractory insert. From the data of height variation with time, the equivalent retardation pressure is determined. The data also provide the calculation of head loss coefficient and constricted stream radius