METHOD OF CONTROLLING THE SOLIDIFICATION STRUCTURE OF A CONTINUOUS-CAST METAL PRODUCT BY ELECTROMAGNETIC AGITATION

摘要

1454704 Continuous casting INSTITUT DE RECHERCHES DE LA SIDERURGIE FRANCAISE 20 May 1974 [21 May 1973] 22376/74 Heading B3F [Also in Division G3] In order to cause movement of metal in the molten core of a solidifying continuous casting 3, e.g. of Ni-Cr steel, at least in a zone of the solidification front to obviate dendritic growth near the axis of the casting; (a) the casting is exposed to a magnetic field at a region of mean level H where the ratio of twice the thickness of the solidified shell to the casting thickness is 1:#2 for a normal withdrawal speed, the action of the magnetic field, e.g. a rotary field provided by an inductor 6 with three bipolar windings with a three-phase supply, is maintained over a distance l, in metres, given by l = KV M where V M is the maximum withdrawal speed in m./min. and K is a constant at least equal to 0.17; (b) the withdrawal speed is measured continuously, e.g. by a detector associated with a withdrawal roller; and (c) the intensity of the magnetic field is regulated as a function of withdrawal speed variation, e.g. by a device regulated by a signal from the detector and controlling the induction coil supply, to maintain constant, between 3À5 and 5À3, a value a given by a=B o .e.#f/p in which B o is the effective value in Tesla of the no-load induction in the region where said zone of the solidification front forms, f is the supply frequency in Hz to the inductor, p is the resistivity of the molten metal in Q m, e is the mean distance between two opposite points of the solidification front in a line perpendicular to the casting surface in the zone of magnetic influence, the distance being given by e = E - 2k#H/V in which, E is the diameter of a reference product of circular section obeying the same law of solidification as the casting, said diameter being equal to the smaller dimension in the case of a non-square rectangular casting, k is a coefficient of solidification of the product, V is the instantaneous withdrawal speed in m./min., and H is the distance in metres between the level H and the level H s where solidification is complete.