| 摘要 |
PURPOSE:To obtain a firm thin protective film having weather resistance simply at low cost by treating a rare earth permanent magnet, a fundamental composition of which consists of a rare earth metal, iron and boron, with steam. CONSTITUTION:A rare earth permanent magnet, a fundamental composition of which is composed of a rare earth metal, iron and boron, is treated with steam. That is, the rare earth permanent magnet is heated, air and heating steam are passed through the permanent magnet, and the permanent magnet is reduced by a reducing gas, thus forming Fe3O4. Consequently, a obtained film has a jet-black color, thin film thickness such as several mum or less and also weather resistance and heat resistance. An Nd-Fe-B magnet is known as the rare earth permanent magnet, but one kind or two kinds or more of rare earth elements such as Y, La, Ce, Pr, etc. may be used as the rare earth metal, sufficient magnetic performance is acquired even by didym (Pr-Nd) and cerium-didym (Ce-Pr-Nd), and these alloys are advantageous from the aspect of supply and cost. A small amount of a heavy rare earth element such as Dy, Tb, etc. is added, thus increasing coercive force iHc, then substantially improving temperature characteristics. |
