New series of Sm_2TM_(17) magnet materials for applications at temperatures up to 550 deg C

摘要

A new series of Sm(Co_wFe_vFCu_xZr_y)_z magnet products with _IH_c up to 13 kOe at 400 deg C has been developed. These magnets have low temperature coefficients of _iH_c and a straight line B vs. H (extrinsic) demagnetization curve up to 550 deg C. A straight line extrinsic curve provides greater design flexibility and facilitates reduced size and weight of magnetic circuits. The straight line extrinsic demagnetization B curves are required for magnets used in dynamic applications. The maximum use temperature, defined here as T_M, can be determined by finding the maximum temperature at which the B curve is a straight line. The results of this work show that increasing the Co content in the magnet enhances high temperature performance. A higher Co content provides a lower temperature coefficient beta of _iH_c. Magnets with Co content w = 0.65 have beta = 0.26percent/deg C from 25 deg C to 300 deg C. Magnets with w = 0.82 have beta = 0.116percent/deg C from 25 deg C to 300 deg C. The lower beta results in a higher (BH)_(max) at high temperature, and a higher T_M. The T_M is 240 deg C for w = 0.65, 330 deg C for w = 0.68, 400 deg C for w = 0.76, 490 deg C for w = 0.78, and 550 deg C for w = 0.82. By increasing the Co content and adjusting the content of other elements, along with appropriate changes of processing parameters, a new series of magnets has been developed for use at temperatures from 400 deg C to 550 deg C. Magnetic properties vs. temperature for the new series of magnets, in comparison to those of the best commercial magnets, are shown in this paper to illustrate the improvements which have been made. Magnetic properties at different temperatures vs. Co content for the series are also reported in this paper.