Takahiro Kan

Ribbon-form silicon-iron alloy containing around 6% silicon

By a roller quenching method, XSi-(100-X)Fe ribbons ( 6.0 \leq X \leq 7.0 ) in the crystalline state were prepared. The size of them was 20 to 150μm in thickness, 2 to 25 mm in width and 5 to 10 m in length, and after annealing all of them were mechanically very soft so as to be bent 180°. In the grain structure of the as-prepared ribbons the columnar grains about 10μm in diameter were observed to grow from the surface to the middle part of the ribbon thickness. The texture of them have

Control of inhibitor precipitation for producing grain-oriented silicon steel

Grain-oriented electrical steels have been widely used for various products, and hence, improving their properties is greatly desired to thus save electricity. Magnetic properties of grain-oriented 3% Si steels have been steadily improved since Goss invented this steel. The authors are convinced that the possibility of further improvement still exists. An important metallurgical basis for producing grain-oriented Si steel is controlling the primary recrystallization texture and the dispersion of inhibitors. Mechanisms of secondary recrystallization and the influence of primary texture on it have been discussed by Harase et al. It is well known that the inhibitor plays its role at the secondary recrystallization stage. Three important metallurgical factors related to the inhibitor exist in the process: dissolution, precipitation, and Ostwald ripening. The most important of these processes is precipitation, which is achieved primarily during hot rolling and comprises a cooling process and a deformation process. The purpose of this article is to clarify the metallurgical sequence of precipitation during hot rolling and then to improve the process by the application of this information to obtain improved magnetic properties.

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.

Magnetic properties of roller-quenched high silicon steel ribbons

Abstract The magnetic properties of high silicon steel ribbons prepared by the roller-quenching method were investigated, and this new material was considered to offer the potential of reducing core losses of electrical machines and power transformers.

Texture improvement in high-permeability nonoriented electrical steel by antimony addition

ConclusionThe mechanism of the significant effect of antimony additions on texture improvement was studied, and the results are as follows. When grain size before cold rolling was small, the antimony addition retarded {111} texture formation in the grain growth stage. When grain size before rolling was large, the {110} component increased in the early stage of recrystallization in the antimony-containing specimens because of the dense formation of deformation bands. Based on these effects of antimony additions on preferential texture formation, high-permeability nonoriented electrical steel has been produced at Kawasaki Steel Corporation.

Influence of toroid radius on magnetic properties of iron-based amorphous alloys and 6.5WT%Si-Fe rapidly solidified ribbons

Iron-bases amorpnous alloys (Fe 78 B 13 Si 9 ), crystalline 6.5wt% Si-Fe rapidly solidified ribbons and 3wt% silicon steel sheets were wound in to toroid cores of 25mm width and 5∼35mm radius. A stress of 130MPa was applied to the amorphous ribbons by 130MPa. The AC and DC properties were measured, and then the magnetic domain configurations were observed by SEM. The iron loss of amorphous alloys increased inversely proportional to the toroid radius before Stress Relief Annealing (SRA), but were almost independent of radius after SRA. The results on 6.5wt%Si-Fe ribbons were similar to those of amorphous ribbons. The increase in losses were due to hysteresis loss in both cores. A similar effect of the toroid radius was shown on the magnetic domain configurations. The 180° and cross domain configurations were observed on both surfaces of flat ribbons before SRA. A wide 180° domain was observed after SRA. When the specimen was bowed to various radii, wide 180° domains were observed in the longitudinal direction on the convex side and narrow 180° domain was observed in the transverse direction on the concave side. The iron loss was reduced by a factor of 2 with increasing applied stress up to 70MPa before SRA and up to 25MPa after SRA.

Control of recrystallization during high-temperature hot-rolling of grain-oriented silicon steel

Recrystallization kinetics of 3 % Si steel after hot rolling in the temperatures between 1373 and 1573 K, which is quite important to obtain uniform magnetic properties, was studied. Recrystallization rate after hot rolling was relatively slow because of low dislocation density, which resulted from rapid recovery, and its behavior was strongly influenced by the initial grain size and coexistence of the γphase. Based on these Findings, controlling technology of recrystallization during hot rolling of grain-oriented Si steels is discussed.

Influence of heat treatment before secondary recrystallization on magnetic properties of 3% Si grain-oriented steel containing Sb

Abstract The secondary recrystallization of 3% Si grain-oriented steel containing Sb has been investigated. The mechanism of the improvement of the magnetic properties under the conditions of Sb addition and a constant temperature treatment during secondary recrystallization has been clarified by three experiments. It has been found that (1) Sb segregation in grain boundaries during decarburization annealing retards decarburization and grain growth, so that the {110} intensity increases and the grain size decreases with increasing Sb; (2) the constant temperature treatment for final annealing enhances the Sb segregation in grain boundaries, and therefore maintains the {110} intensity in the specimen with the addition of Sb; and (3) the addition of Sb increases the inhibiting force. These three effects enable secondary recrystallization such that many (110)[001] nuclei grow rapidly, surrounded by small primary grains, leading to high B 8 values.

Investigation on the domain refining effect in grain-oriented silicon steel

Conditions to maximize the domain refining effect were investigated using the plasma flame irradiation method. It was required to optimize the interval of plasma flame irradiated lines depending on the grain size of the sheet and to reduce the tilt angle of the sheet.

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.