Abstract
Nd-Fe-B alloy powder was granulated by a spray drying method using organic binder consisted of polyvinylalcohol or cellulose ethers, in order to improve the powder flowability during feeding and compacting. The compressing behavior of Nd-Fe-B granulated powders was investigated. In the case of granulated powders, the relation between compressing stress and powder bulk density was expressed by two straight lines containing one bending point, and the compressing stress on this point was defined as the average destruction strength(ADS). The ADS was closely related with the tensile strength of organic binder. By means of controlling the tensile strength of binder by changing its composition or polymer/plasticizer ratio, the ADS could be designed easily. In the case that the ADS was less than about 0.1N/mm2, the powder flowability of granulated powder was improved with increasing the ADS, whereas in the case of more than about 0.1N/mm2, it showed almost constant value. The magnetic characteristics (remanences and maximum energy product) of sintered magnets using granulated powders were improved proportionally with decreasing the ADS, which was independent of any kinds of polymers and binder composition. These facts mean that the degree of the magnetic orientation of primary particles in granulated powders under a magnetic field can be determined simply by the ADS.
