Manabu Ueno

Characteristic evaluation of steel roof sheet for snow sliding. Part 2. Secular changes of steel roof sheets for snow sliding.

多雪地帯で使われる代表的な種類の屋根鋼板について, 滑雪性の評価パラメーターである氷と鋼板間の静・動摩擦係数, それに関わる鋼板表面の組織, 表面あらさおよび光沢度の経年変化を調べた.その結果, これら表面特性は相互に密接に関連していることが明らかとなった.また, 硬い雪に対する摩擦特性は氷に対するそれと相似していること, および経年変化後も静摩擦係数は動摩擦係数と線形関係にあることを示した.さらに, 氷と鋼板間の摩擦係数を用いた滑雪性の経年変化の予測を行ったところ, 3シーズンに至る大気暴露試験結果と良く対応した.このことより初期摩擦係数のみならず摩擦係数の経年変化率が共に小さい鋼板ほど, 経年後も滑雪性に優れていると結論した.

Production of fine aluminum powders by gas bubbling atomization process.

A new type atomization technique for aluminum powders is proposed. In this process, the bubbles produced by the ejection of Ar gas into molten metal atomize it to fine liquid particles, which reach upper rotating disk cooled with liquid N2, and are crushed into the finer solid particles. The obtained aluminum powders were polycrystalline, and their shapes were very irregular. The size of particles was distributed at value between 0.5 and 10 μm. A mean particle size of the powder decreased with lowering atomization temperature and with increasing discharge of Ar gas and rotational speed of the disk. Nozzle diameter also influenced delicately on the distribution of particle size.