The Variation of Magnetic Properties of Fe-Based Amorphous Alloys Along the Ribbon Length
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THE VARIATION OF MAGNETIC PROPERTIES OF Fe-BASED AMORPHOUS ALLOYS ALONG THE RIBBON LENGTH TAKASHI SATO,
TSUTOMU OZAWA, TOSHIO YAMADA and RYUTARO MATSUMOTO
Fundamental Research Laboratories, Nippon Steel Corporation, 1618, Ida, Nakahara, Kawasaki, Japan.
ABSTRACT The variation of ac magnetic properties along the length of melt-spun Fe-based amorphous ribbons was examined in relation to the variations of the roller surface temperature and the ribbon thickness. The results indicated that the lengthwise variation of magnetic properties strongly depends both on the roller surface temperature and the ribbon thickness. The critical cooling rates at which core loss begins to increase were determined from the relationship between core loss and cooling rate. For ribbons cast at lower cooling rate than critical cooling rate, the finedomain patterns were usually observed on the free surface. From the disappearance of the fine-domain pattern and the remarkable decrease of core loss by removal of the surface layers, it is ascertained that the surface layers deteriorate magnetic properties.
INTRODUCTION It is well known that magnetic and mechanical properties of melt-spun amorphous alloys vary along the ribbon length and width, and that the variation increases with increasing ribbon length and width. The magnetic properties probably becomes more sensitive to the variation of process variables with increasing ribbon sizes due to the rise in the roller surface temperature. There have been many reports describing the effect of process variables on melt-spun ribbon properties, but no reports concerning the effect of the roller surface temperature on the variation of magnetic properties as far as we know. In the present paper, we will describe the effect of the roller surface temperature during the ribbon preparation and the ribbon thickness on the variation of ac magnetic properties along the ribbon for Fe-based amorphous alloys. These two factors are taken as important factors reflecting the variation of process variables. EXPERIMENTAL Fe-based amorphous alloy ribbons with various compositions were prepared by melt spinning method using a single steel roller equipment without a water cooling system. All the ribbons were 20 mm wide and 50 - 100 m long. The thicknesses calculated from ribbon weight and density were varied within ±15% along the ribbon. The roller surface temperature was measured by a radiation thermometer located about 10 cm behind the nozzle as shown in Fig. 1. The core loss and induction were measured under sinusoidal flux condition on 20 nmwide and 120 mm long straight samples taken at intervals of every 5 meters with a single strip tester. The values of core loss were reduced to those of 30 pm in thickness using the core loss vs thickness relationship. Magnetic domain observation, and X-ray diffraction and magnetic torque measurements were carried out in order to clarify the relation between the magnetic properties and the structure.
206 RESULTS AND DISCUSSION Variation profiles of magnetic properties al
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