GB738622A - Fluid stirring apparatus - Google Patents

Abstract

738,622. Stirring appliances. BABCOCK & WILCOX CO. Aug. 10, 1953 [Aug. 14, 1952], No. 22069/53. Class 86. [Also in Groups XI, XII and XXXV] A device for stirring electrically-conductive fluid material consists of a rotatable magnetic field member including a succession of peripherally-disposed magnetic poles of alternately opposite polarities and having a peripheral pole pitch of such length that, on operation of the field member, a moving field of substantial strength penetrates into the fluid material disposed closely adjacent the rotatable field member, and a shroud of non-magnetic material surrounding the field member. As described, molten metal in tiltable ladle 4 (see Group XII), is circulated along a path 41 under the influence of a rotating electromagnetic field member 30 having peripherally disposed poles 40, situated adjacent an upwardly sloping portion 32 of the bottom of the ladle. The ladle consists of a refractory lining 8 within a metal support structure 7 of which the bottom 33 is given a high resistance to eddy currents, as by employing a slotted, laminated or slatted construction in metal of high resistivity. The bottom 33 may be of non-magnetic metallic material, such as stainless steel. If desired, the horizontal portion of the bottom 33 may be made highly electrically and magnetically conductive to screen the rear portion of the bath 9 against the inductive effect of the magnet 30 to prevent reverse flow up the rear wall of the ladle. The field member 30 is peripherally surrounded by a thin non-magnetic open-ended cylindrical metal shroud 65 through which cooling air is drawn by a fan rotating coaxially with the field member 30. A non-magnetic scraper 66 keeps the shroud 65 clear of foreign iron or steel material. The windings of the field member 30 are excited by current supplied through sliprings from a battery and rheostat, Fig. 2 (not shown). During pouring of the metal through the spout 11 the windings of the field member 30 may be overloaded to produce a stronger stirring action which keeps the surface slag away from the pouring spout 11. The ladle 4 is provided with heating electrodes 10. In a modification, Fig. 3 (not shown), the rotatable field member is located beneath an arch formed in the bottom of a shallow melting furnace, and with an elongated furnace, two or more spaced, similarly-arranged inductors could be used.