Coating Method and Apparatus, a Permanent Magnet, and Manufacturing Method Thereof

Abstract

A film is formed at a high rate on the surface of an iron-boron-rare-earth-metal magnet having a given shape, while effectively using dysprosium or terbium as a film-forming material. Thus, productivity is improved and a permanent magnet can be produced at low cost. A permanent magnet is produced through a film formation step in which a film of dysprosium is formed on the surface of an iron-boron-rare-earth-metal magnet of a given shape and a diffusion step in which the magnet coated is subjected to a heat treatment at a given temperature to cause the dysprosium deposited on the surface to diffuse into the grain boundary phase of the magnet. The film formation step comprises: a first step in which a treating chamber where this film formation is performed is heated to vaporize dysprosium which has been disposed in this treating chamber and thereby form a dysprosium vapor atmosphere having a given vapor pressure in the treating chamber; and a second step in which a magnet kept at a temperature lower than the internal temperature of the treating chamber is introduced into this treating chamber and the dysprosium is selectively deposited on the magnet surface based on a temperature difference between the treating chamber and the magnet until the magnet temperature reaches a given value.

1 . A coating method comprising
 a first step for heating a process chamber and generating metallic vapor atmosphere within the process chamber by vaporizing vaporizable metallic material previously arranged within the process chamber, and   a second step for introducing into the process chamber articles to be coated held at a temperature lower than that within the process chamber and then selectively depositing the vaporizable metallic material on a surface of article to be coated by an effect of temperature difference between the temperature within the process chamber and that of the articles to be coated.   
     
     
         2 . A coating method of  claim 1  wherein the metallic vapor atmosphere is in a saturated condition within the process chamber. 
     
     
         3 . A coating apparatus comprising
 a process chamber which can heat substantially uniformly an inside of the process chamber to a high temperature by a heating means,   a preparatory chamber communicating to the process chamber,   an evacuating means for holding both the process and preparatory chambers at a predetermined degree of vacuum,   an open/close means moveable between an opened position in which the process and preparatory chambers are communicated each other and a closed position in which the process chamber is tightly closed, and   a conveying means which can move the articles to be coated between the process chamber and the preparatory chamber and can tightly close the process chamber when the articles to be coated are moved into the process chamber at the opened position of the open/close means,   wherein the process chamber is heated at the closed position of the open/close means, metallic vapor atmosphere is generated by vaporizing vaporizable metal material previously arranged within the process chamber, the articles to be coated within the preparatory chamber are moved into the process chamber by the conveying means with the open/close means being moved to the opened position so as to selectively deposit the vaporizable metallic material on a surface of article to be coated by an effect of temperature difference between the temperature within the process chamber and that of the articles to be coated.   
     
     
         4 . A coating apparatus of  claim 3  wherein the process chamber is arranged within a vacuum chamber equipped with another evacuating means and defined by a uniformly heating plate formed with an opening at one side thereof, a heat insulating member is arranged so that it encloses the uniformly heating plate except for said side of the uniformly heating plate in which said opening is formed, and a heating means for heating the uniformly heating plate is arranged between the uniformly heating plate and the heat insulating member. 
     
     
         5 . A coating apparatus of  claim 3  further comprising a gas introducing means for introducing inert gas into the preparatory chamber, and the inert gas is introduced into the preparatory chamber via the gas introducing means so as to hold the pressure within the process chamber at a negative pressure relative to that of the preparatory chamber. 
     
     
         6 . A coating apparatus of  claim 3  wherein the preparatory chamber is equipped with a gas introducing means for introducing He gas into the preparatory chamber, and the He gas is introduced into the preparatory chamber via the gas introducing means so as to hold the pressure within the process chamber at substantially same as that within the preparatory chamber. 
     
     
         7 . A coating apparatus of  claim 6  wherein the process chamber is arranged below the preparatory chamber. 
     
     
         8 . A coating apparatus of  claim 3  further comprising a placement means on which the vaporizable metallic material can be placed within the process chamber, and the placement means is formed as an annulus so that the vaporizable metallic material can be arranged around the articles to be coated when the articles to be coated are moved into the process chamber by the conveying means. 
     
     
         9 . A coating apparatus of  claim 3  wherein the preparatory chamber is equipped with a plasma generating means for cleaning the surface of article to be coated by using plasma. 
     
     
         10 . A coating apparatus of  claim 3  wherein the preparatory chamber is equipped with another heating means for cleaning the surface of article to be coated by heat treatment with introducing the inert gas into the vacuum atmosphere or the preparatory chamber via the gas introducing means connected thereto. 
     
     
         11 . A coating apparatus of  claim 3  wherein the vaporizable metallic material is alloy including either one of Dy or Tb or including at least one of Dy and Tb, and the article to be coated is a sintered magnet of Fe—B-rare earth elements having a predetermined configuration. 
     
     
         12 . A method for manufacturing a permanent magnet comprising steps for coating vaporizable metallic material including at least one of Dy and Tb on a surface of a magnet of Fe—B-rare earth elements having a predetermined configuration, and diffusing the vaporizable metallic material coated on the surface of the magnet into crystal grain boundary phases of a sintered magnet by heat treating the vaporizable metallic material at a predetermined temperature characterized in that the coating step comprises a first step for heating a process chamber used for carrying out the coating step and generating metallic vapor atmosphere within the process chamber by vaporizing vaporizable metallic material previously arranged within the process chamber, and a second step for introducing into the process chamber the magnet held at a temperature lower than that within the process chamber and then selectively depositing the vaporizable metallic material on a surface of the magnet by an effect of temperature difference between the temperature within the process chamber and that of the magnet by the magnet reaches a predetermined temperature. 
     
     
         13 . A method for manufacturing a permanent magnet of  claim 12  wherein the metallic vapor atmosphere is in a saturated condition within the process chamber. 
     
     
         14 . A method for manufacturing a permanent magnet of  claim 12  wherein the vaporizable metallic material further includes at least one of Nd, Pr, Al, Cu, Ga and Ta. 
     
     
         15 . A method for manufacturing a permanent magnet  claim 12  wherein the predetermined temperature in the second step is lower than 250° C. or higher than 450° C. 
     
     
         16 . A method for manufacturing a permanent magnet  claim 12  further comprising a step for cleaning the surface of the magnet within the vacuum atmosphere prior to introduction into the process chamber of the magnet held at a temperature lower than that within the process chamber. 
     
     
         17 . A method for manufacturing a permanent magnet  claim 12  wherein the temperature within the process chamber in the first step is set at a range of 1,000˜1,700° C. 
     
     
         18 . A method for manufacturing a permanent magnet  claim 12  wherein the grain diameter of the vaporizable metallic material arranged within the process chamber in the coating step is in a range of 10˜1,000 μm. 
     
     
         19 . A permanent magnet comprising a magnet of Fe—B-rare earth elements having a predetermined configuration, and a surface of the magnet being selectively deposited by the vaporizable metallic material by an effect of temperature difference between the temperature within the process chamber and that of the magnet by the magnet reaches a predetermined temperature with generating metallic vapor atmosphere within the process chamber by vaporizing vaporizable metallic material including at least one of Dy and Tb and with introducing into the processing chamber the magnet held at a temperature lower than that within the process chamber, then the magnet being heat treated so as to diffusing at least one of Dy and Tb on the surface of the magnet into crystal grain boundary phases of the magnet. 
     
     
         20 . A permanent magnet of  claim 19  wherein the surface and crystal grain boundary of the magnet have a rich phase including at least one of Dy and Tb. 
     
     
         21 . A permanent magnet of  claim 19  wherein the surface of the magnet is covered by the rich phase, and the crystal grain boundary includes 1˜50% rich phase.