Alloy flake for rare earth magnet, production method thereof, alloy powder for rare earth intered magnet, rare earth sintered magnet, alloy powder for bonded magnet and bonded magnet

A mixed powder for a rare earth sintered magnet produced by mixing a main phase alloy for a rare earth magnet according to any one of 1 to 3 with a boundary phase alloy which has an R content higher than that of the main phase alloy and has a Pr content of R lower than that of the main phase alloy.

A rare earth magnet alloy flake comprising an R-T-B alloy (R represents at least one rare earth element including Y;

• T represents transition metals including Fe as an essential element;
• and B represents boron), characterized in that the flake has a thickness falling within a range of 0.1 mm to 0.5 mm, and that at least one surface of the flake has a surface roughness, as represented by 10-point average roughness (Rz), falling within a range of 5 μm to 50 μm.

A method for producing a rare earth magnet alloy flake formed of an R-T-B alloy including a strip casting method, characterized by comprising adjusting the surface roughness, as represented by 10-point average roughness (Rz), of the cast surface of a rotating roller for casting to fall within a range of 5 μm to 100 μm.

A method for producing a rare earth magnet alloy flake according to any one of 13 to 15 formed of an R-T-B alloy including a strip casting method, characterized by comprising adjusting the surface roughness, as represented by 10-point average roughness (Rz), of the cast surface of a rotating roller to fall within a range of 5 μm to 100 μm.

A rare-earth-containing alloy flake, characterized in that the alloy flake has a thickness falling within a range of 0.1 mm to 0.5 mm, at least one surface of the alloy flake has a plurality of elongated raised/dented segments (i.e., small ridge/valley areas) formed so as to cross one another, and the surface having the elongated raised/dented segments has a surface roughness, as represented by 10-point average roughness (Rz), falling within a range of 3 μm to 30 μm.

A method for producing a rare-earth-containing alloy flake including a strip casting (SC) method, characterized by comprising employing a rotating roller for casting, the roller having, on the cast surface, a plurality of elongated raised/dented segments formed so as to cross one another and having a surface roughness of the cast surface, as represented by 10-point average roughness (Rz), falling within a range of 3 μm to 30 μm.

An alloy powder for a rare earth sintered magnet produced by subjecting, to a hydrogen decrepitation step, a rare-earth-containing alloy flake as recited in (24) or (25), followed by pulverization by means of a jet mill.

An alloy powder for a bonded magnet produced by use of a rare-earth-containing alloy flake as recited in (24) or (25) through an HDDR method.

A method for producing a rare-earth-containing alloy flake including a strip casting method, characterized by comprising employing a rotating roller for casting, the roller having, on the cast surface, a plurality of elongated raised/dented segments and having a surface roughness provided by a plurality of elongated raised/dented segments, as represented by 10-point average roughness (Rz), falling within a range of 3 μm to 60 μm, 30% or more of raised/dented segments among entire elongated raised/dented segments extending in a direction forming an angle of 30° or more to a roller rotation direction.