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We investigated the fabrication of melt-textured Gd-Ba-Cu-O bulk superconductors with the employment of a Gd 2 BaO 4 (Gd210)-BaCuO 2 -CuO precursor. This enabled us to synthesize a very large Gd-Ba-Cu-O bulk superconductor, 140 mm in diameter. The trapped field distribution measured at 77 K revealed that the sample had no serious cracks, and the maximum field was 2.3 T. The formation behaviour and depressing mechanism of cracking were studied using sintered Gd210-containing precursors. The Ba-Cu-O component in the precursor melted at around 900 • C. The formation of such a liquid phase enhanced the densification of the precursor by liquid phase sintering. The mechanical strength of the sintered precursor was increased compared to the conventional Gd123-Gd211 precursor. This will be effective in preventing crack formation in the texturing process of large single-grain samples. The superconducting properties of the bulk sample fabricated from Gd210-containing precursor have been discussed.

Tests to measure the effects of the precipitating size of Cu on the magnetic properties of nongrain-oriented (NGO) electrical steel were carried out. The hysteresis loss had a maximum value when the diameter of the precipitates was around the thickness of the domain wall and decreased rapidly with decreasing size of the precipitates. Alternatively, yield point (YP) rose steeply with reduction in the size of Cu precipitates. It can be confirmed that the precipitating Cu has an ability of rising over 100 MPa in YP without deteriorating core loss. Regarding the effects of Cu precipitates on the hysteresis loss, the surface tension effect might be dominant for the case in which precipitates are smaller than the domain wall thickness, and internal magnetic poles are effective for the larger precipitates.Index Terms-Domain wall pinning, high tensile strength steel, precipitation hardening, Si-Fe.

This paper discusses the deterioration mechanism of magnetic properties of cores due to punching and proposes the modeling, as the best design of motors, considering manufacturing motors, is important in order to improve the high performance of motors corresponding to energy saving. In producing motors, magnetic cores with laminated steel sheets are made of punched sheets, and then the magnetic properties of steel sheets are deteriorated by plastic deformation and the induced residual stress due to punching. In this paper, the punching deterioration mechanism is investigated by observing magnetic domains at steel surfaces near sheared parts. Tensile and compressive stresses induced at cut steel edges deteriorate the magnetic properties of punched steel sheets in high flux densities as the compression deterioration is stronger than the tension improvement, and improve permeabilities at low magnetic field because the increases in permeabilities with tensile stresses are emphasized. Therefore, it is necessary to model the magnetic properties of motor magnetic cores, taking account of these magnetic phenomena.