Abstract: A heat flux derivation unit (202) derives a value qy of a y-axis direction component of a heat flux vector. A molten metal surface level derivation unit (203) derives, as a molten metal surface level, a position where the absolute value of the value qy of the y-axis direction component of the heat flux vector whose y-axis component vector is in a direction opposite to a casting direction is maximum.

Abstract: A heat flux derivation unit (202) derives a value qy of a y-axis direction component of a heat flux vector. A molten metal surface level derivation unit (203) derives, as a molten metal surface level, a position where the absolute value of the value qy of the y-axis direction component of the heat flux vector whose y-axis component vector is in a direction opposite to a casting direction is maximum.

Abstract: The present invention provides a Fe—B—Si system amorphous alloy thin strip excellent in high magnetic flux density, thermal stability, amorphous formability improved workability and low core loss. The present invention further provides a Fe—B—Si system amorphous alloy thin strip which has the reduced cost without using high purity iron resources such as an electrolytic iron as iron resources used in an amorphous alloy thin strip, and also has core loss less than 0.10 W/kg at W13/50 in soft magnetic property in alternating-current field. The Fe—B—Si system amorphous alloy thin strip according to the present invention contains an appropriate amounts of N, C, P to improve thermal stability, amorphous formability, workability (brittleness), and core loss without deteriolating magnetic flux density, and contains, in atomic %, B: 5-25%, Si: 1-30%, N: 0.001-0.2%, C: 0.003-10%, P: 0.001-0.

Abstract: The present invention provides a Fe—B—Si system amorphous alloy thin strip excellent in high magnetic flux density, thermal stability, amorphous formability improved workability and low core loss. The present invention further provides a Fe—B—Si system amorphous alloy thin strip which has the reduced cost without using high purity iron resources such as an electrolytic iron as iron resources used in an amorphous alloy thin strip, and also has core loss less than 0.10 W/kg at W13/50 in soft magnetic property in alternating-current field. The Fe—B—Si system amorphous alloy thin strip according to the present invention contains an appropriate amounts of N, C, P to improve thermal stability, amorphous formability, workability (brittleness), and core loss without deteriolating magnetic flux density, and contains, in atomic %, B: 5-25%, Si: 1-30%, N: 0.001-0.2%, C: 0.003-10%, P: 0.001-0.