Kiyoshi Shibuya

Development of a rapid solidification process with a double-roller method

Abstract A thin strip caster has been developed which consists of twin cooling rollers, a secondary cooling zone, tension control systems and a continuous-coiling machine. With this caster, fine crystalline strips were continuously produced to a near-net shape whose dimensions were 0.2–1 mm in thickness, 250–500 mm in width and 500 kg in unit coil mass. The characteristics of the thin strip caster are as follows. 1. (1) Many types of metal alloy whose melting points are less than 1800 K are rapidly solidified. 2. (2) Materials with a difficult workability, such as high silicon steel or high alloy stainless steel, are coiled in a net shape or near-net shape. 3. (3) Because of the cooling rate which is of the order of 102 K s−1 in a secondary cooling zone, the coils have such advantages of the rapid solidification process as a fine crystalline structure or decreased precipitation.

ANALYSIS OF THE SOLIDIFICATION PROCESS IN THE ROLLER QUENCHING METHOD

High silicon steel ribbons with 4.5–6.5 wt% Si were produced by single- and double-roller methods. The solidification parameters were in good agreement with those obtained by computer simulation with the suitable thermal parameters. Following these results, the melt-puddle stability was discussed.

Conduction and magnetic properties of FeBSi amorphous alloy ribbons: a review

Abstract Amorphous alloy transformers have demonstrated satisfactory technical performance in numerous field trials, but amorphous alloys still have several drawbacks in comparison with grain-oriented silicon steels. In particular, the brittleness of amorphous materials causes problems during the manufacture of transformers, and the local brittle regions which occur in the casting of wide ribbons contain medium-range-ordered clusters 2–3 nm in size, which characteristically lead to quality problems, by causing the area of embrittlement to spread during annealing. The brittleness of amorphous ribbons is investigated in terms of (1) inadequate cooling in the casting processes, (2) impurities in the molten metal, and (3) inappropriate annealing conditions.