SPINNING CONDITION, STRUCTURE AND MAGNETI C-PROPERTIES OF FE-6.5 MASS-PERCENT-SI ALLOY FIBER PRODUCED BY THE IN-ROTATING-LIQUID-SPINNING PROCESS

Almost zero magnetostrictive Fe-6.5 mass%Si alloy fibers less than abo ut 90 mu m in diameter, having a large Barkhausen effect in magnetic p roperties were obtained by using the laboratory scale, the In-Rotating -Liquid-Spinning Process (INROLISP). The spinning conditions, jet stab ility, morphology of dendritic growth and magnetic properties were dis cussed for the fiber about 70 mu m in diameter from the manufacturing viewpoint. In the case of spinning speeds of less than about 10 m/s, t he jet bounced on the surface of rotating liquid, such as water, water with chemicals lowering surface tension, and some oils. Over 10 mis, the jet subsequently penetrated under the liquid surface after an inte rval of around 100 ms from ejecting start. The centrifugal force effec t was considered in this phenomenon. When the jet bounced, in some par t of the fiber structure, primary dendrite arms growing uniformly alon g the fiber direction were observed. In another part, however, the dir ection of the primary arm changing gradually far from the fiber axis a nd the secondary arm becoming the primary grown to the fiber axis was observed without clear grain boundary. It is considered that the curva ture of the bouncing jet at the ejection point obstructs the primary a rms growing in a straight line. When jet penetrated, the ''bamboo stru cture'' was observed in the fiber structure. The penetrating jet forme d the cavity of the coolant at its downstream from the jet. It means t hat the penetrating jet at first goes through the non-contacting area to the coolant at the cavity side and the contacting area to the coola nt at the opposite side. Therefore, the primary arms tend to grow from the contact to the cavity sides. By the zone-annealing process, it wa s difficult to make any fiber a fairly long single crystal. In order t o control the continuous growth of the primary arms toward the fiber d irection, it was suggested that the process which is able to cool the jet uniformly around its circumference and make the primary arms grown in a straight jet is needed. The necessary conditions to produce a fi ber having the large Barkhausen effect in this alloy, were the nearly unidimensional shape and a [100] crystal direction of arpha-phase para llel to the long axis. Furthermore, to obtain an ideal rectangular hys teresis loop, the cross-sectional round shape, the absence of residual stress and precipitation was suggested.