Permanent magnet with good thermal stability
AssigneeHitachi Metals, Ltd.
InventorsMinoru Endoh, Masaaki Tokunaga, Hiroshi Kogure
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Abstract
A permanent magnet having good thermal stability, consisting essentially of the composition represented by the general formula: R(Fe.sub.1-x-y-z Co.sub.x B.sub.y Ga.sub.z).sub.A wherein R is Nd alone or one or more rare earth elements mainly composed of Nd, Pr or Ce, 0.ltoreq.x.ltoreq.0.7, 0.02.ltoreq.y.ltoreq.0.3, 0.001.ltoreq.z.ltoreq.0.15 and 4.0.ltoreq.A.ltoreq.7.5. This permanent magnet may contain one or more additional elements selected from Nb, W, V, Ta and Mo. This permanent magnet has high coercive force and Curie temperature and thus highly improved thermal stability.
Claims11
In sintered magnets having a composition of
- (R.sub.1-a R*.sub.a)(Fe.sub.1-x-y-u Co.sub.x B.sub.y M.sub.u).sub.A
- where R and R* are light and heavy rare earth elements, respectively,
- the improvement comprising selecting M to be Nb,
- R to be Nd or a mixture of Nd and Pr,
- R* to be Dy,
- .ltoreq. a.ltoreq.0.25,
- 0.ltoreq.x.ltoreq.0.4,
- 0.02.ltoreq.y.ltoreq.0.3,
- 0.001.ltoreq.u.ltoreq.0.1, and
- 4.0.ltoreq.A.ltoreq.7.5,
- the improvement further comprising the substitution of 0.001 to 0.15 of Fe with Ga for increasing the intrinsic coercivity and decreasing the irreversible loss of flux at elevated temperature, and wherein the intrinsic coercivity of the improved magnet is equal to or greater than 16.0 kOe.
In sintered magnets having a composition of
- R(Fe.sub.1-x-y-u Co.sub.x B.sub.y M.sub.u).sub.A
- the improvement comprising M to be one or a mixture from the group consisting of Nb, W, V, Ta, and Mo,
- R to be Nd alone or one or more light rare earth elements selected from the group consisting of Nd, Pr, and Ce, part of which may be substituted by one or more heavy rare earth elements selected from the group consisting of Dy, Tb and Ho,
- 0.ltoreq.x.ltoreq.0.7,
- 0.02.ltoreq.y.ltoreq.0.3,
- 0.001.ltoreq.u.ltoreq.0.1, and
- 4.0.ltoreq.A.ltoreq.7.5,
- the improvement further comprising the substitution of 0.001 to 0.15 of Fe with Ga, for increasing the intrinsic coercivity and decreasing the irreversible loss of flux at elevated temperatures,
- wherein the intrinsic coercivity of the magnet is .gtoreq.15.0 kOe, and
- wherein the irreversible loss of flux of said permanent magnet is less than that of said magnet having Ga along or M alone when measured at the same temperature.
A sintered permanent magnet having high intrinsic coercivity and good thermal stability in terms of low irreversible loss of flux at elevated temperatures, consisting essentially of the composition represented by the general formula:
- R(Fe.sub.1-x-y-z-u Co.sub.x B.sub.y Ga.sub.z M.sub.u).sub.A
- wherein R is Nd alone or a mixture of Nd and one or more light rare earth elements selected from the group consisting of Nd, Pr and Ce, part of which may be substituted by one or more heavy rare earth elements selected from the group consisting of Dy, Tb and Ho, M is one or more elements selected from Nb, W, V, Ta and Mo, and 0.ltoreq.x.ltoreq.0.7, 0.02.ltoreq.y.ltoreq.0.3, 0.001.ltoreq.z.ltoreq.0.15, 0.001.ltoreq.u.ltoreq.0.1 and 4.0.ltoreq.A.ltoreq.7.5, wherein the intrinsic coercivity of the magnet is .gtoreq.15.0 kOe.
Dependencies are inferred from the claim text.