| 摘要 |
<p>PURPOSE:To reduce friction when a magnetic tape slides, by obtaining an occupation ratio of a beta phase to an alpha phase on the outer circumferential surface of a guide cyinder greater than said ratio in said guide cylinder. CONSTITUTION:Molten silicon aluminum alloy consisting essentially of aluminum and additive metals, such as silicon, copper and magnesium, at an adequate mixing ratio is cast in a mold. In this case, a cooling speed is relatively slow and deposition is performed for segregation of a beta phase in the grain boundary of an alpha phase. Specially, the cooling speed of the outer circumferential surfaces of guide cylinders 2a and 2b is made lower than that of the inner circumferential surfaces to achieve the segregation of the beta phase more near the outer circumferential surfaces. Consequently, the beta phase exposed more on the outer circumferential surfaces of the guide cylinders which are tape sliding surfaces, so a coefficient of friction to a magnetic tape is reduced greatly.</p> |
