We report the magnetic field dependence of the critical solidification rate for the stability of liquid-solid interfaces. For a certain temperature gradient, the critical solidification rate first increases, then decreases, and subsequently increases with increasing magnetic field. The effect of the magnetic field on the critical solidification rate is more pronounced at low than at high temperature gradients. The numerical simulations show that the magnetic-field dependent changes of convection velocity and contour at the interface agree with the experimental results. The convection velocity first increases, then decreases, and finally increases again with increasing the magnetic field intensity. The variation of the convection contour at the interface first decreases, then increases slightly, and finally increases remarkably with increasing the magnetic field intensity. Thermoelectromagnetic convection (TEMC) plays the role of micro-stirring the melt and is responsible for the increase of interface stability within the initially increasing range of magnetic field intensity. The weak and significant extents of the magneto-hydrodynamic damping (MHD)-dependent solute build-up at the interface front result, respectively, in the gradual decrease and increase of interfacial stability with increasing the magnetic field intensity. The variation of the liquid-side concentration at the liquid-solid interface with the magnetic field supports the proposed mechanism.

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Abstract. The flow pattern and velocity distribution of liquid metal in the Narrow-Side-Patter-Mold (NSP-Mold) have been investigated with a mercury model as analogue to molten steel in the continuous casting. The Ultrasonic Doppler Velocimeter (UDV) has measured the velocity under various magnetic distribution and flux density. The impingement intensity of liquid metal to mold narrow wall have been calculated based on the measured data, and the influence of magnetic flux density on the liquid metal flow in the mold has been analyzed. The results show that with narrow-side-patter magnet and increase of the magnetic field, the surface of the melt gets weak and the free surface fluctuation is suppressed, the impingement intensity of liquid metal to mold narrow wall gets weak, impacting depth becomes shallow and a plug flow can be rapidly formed.