Santoku Corporation

Takuya Onimura

Shinya Tabata

Kazumasa Shintani

Provided are raw material alloy flakes for a rare earth sintered magnet and a method for producing the same. The alloy flakes have a roll-cooled face, and (1) contain at least one R selected from rare earth metal elements including Y, B, and the balance M including iron, at a particular ratio; (2) as observed in a micrograph at a magnification of 100&#xd7; of its roll-cooled face, have not less than 5 crystals each of which is a dendrite grown radially from a point of crystal nucleation, and crosses a line segment corresponding to 880 &#x3bc;m; and (3) as observed in a micrograph at a magnification of 200&#xd7; of its section taken generally perpendicularly to its roll-cooled face, have an average distance between R-rich phases of not less than 1 &#x3bc;m and less than 10 &#x3bc;m.

Alloy flakes as starting material for rare earth sintered magnet and method for producing same

Provided are alloy flakes for rare earth sintered magnet, which achieve a high rare earth component yield after pulverization with respect to before pulverization and a uniform particle size after pulverization, and a method for producing such alloy at high energy efficiency in an industrial scale. The method includes (A) preparing an alloy melt containing R composed of at least one element selected from rare earth metal elements including Y, B, and the balance M composed of Fe, or of Fe and at least one element selected from transition metal elements other than Fe, Si, and C, (B) rapidly cooling/solidifying the alloy melt to not lower than 700&#xb0; C. and not higher than 1000&#xb0; C. by strip casting with a cooling roll, and (C) heating and maintaining, in a particular temperature range, alloy flakes separated from the roll by rapid cooling and solidifying in step (B) before the flakes are cooled to not higher than 500&#xb0; C., to obtain alloy flakes having a composition of 27.0 to 33.0 mass % R, 0.90 to 1.30 mass % boron, and the balance M.

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Kobe, Japan

Takuya Onimura