Method of pressing rare earth alloy magnetic powder

Abstract

A green compact of a rare earth alloy magnetic powder is made by pressing the powder. The powder is pressed within an air environment that has a temperature controlled at 30° C. or less and a relative humidity controlled at 65% or less.

What is claimed is:  
     
         1 . A method of forming a green compact of a rare earth alloy magnetic powder comprising the steps of: 
 providing a rare earth alloy powder,    providing a controlled environment having a temperature of 30° C. or less and a relative humidity of 65% or less in a space that is large enough for a human being to work therein, said environment including at least an oxygen gas and being breathable by the human being, and    pressing the rare earth alloy powder within the controlled environment in the space.    
     
     
         2 . A method of forming a green compact of a rare earth alloy magnetic powder comprising the steps of: 
 providing a rare earth alloy powder,    providing a controlled environment having a temperature of 30° C. or less and a dew point of at least 6° C. less than the temperature in a space that is large enough for a human being to work therein, said environment including at least an oxygen gas and being breathable by the human being, and    pressing the rare earth alloy powder within the controlled environment in the space    
     
     
         3 . The method of  claim 1  or  2 , further comprising the steps of 
 solidifying a molten alloy at a rate from 10 2 ° C./sec to 10 4 ° C./sec to form the provided rare earth alloy.  
 
     
     
         4 . The method of  claim 3 , wherein the solidified alloy is a rare earth alloy with a thickness between 0.03 mm and 10 mm, and includes R 2 T 14 B crystal grains (where R is a rare earth element, T is either iron or a compound of iron and a transition metal element in which iron is partially replaced with the metal element, and B is boron) and R-rich phases, the sizes of the R 2 T 14 B crystal grains being from 0.1 μm through 100 μm in a minor axis direction and from 5 μm through 500 μm in a major axis direction, the R-rich phases dispersed around a boundary of the R 2 T 14 B crystal grains.  
     
     
         5 . The method of  claim 1  or  2 , further comprising the step of adding a lubricant to the rare earth alloy powder prior to said pressing step.  
     
     
         6 . The method of  claim 1  or  2 , further comprising the step of providing rare earth alloy powder containing oxygen at 6,000 ppm or less.  
     
     
         7 . The method of  claim 3 , further comprising the step of forming an oxide layer on the surface of particles of the rare earth alloy powder by performing said pulverizing step in a jet mill with a controlled concentration of an oxidizing gas.  
     
     
         8 . The method of  claim 1  or  2 , wherein in said step of providing a controlled environment, the controlled environment has a temperature of at least 5° C. and a relative humidity of at least 40%.  
     
     
         9 . The method of  claim 8 , wherein in said step of providing a controlled environment, the controlled environment has a temperature of 15° C.-25° C. and a relative humidity of 40%-55%.  
     
     
         10 . The method of  claim 2 , wherein in said step of providing a controlled environment, the controlled environment has a temperature of at least 5° C.  
     
     
         11 . The method of  claim 10 , wherein in said step of providing a controlled environment, the controlled environment has a temperature of 15° C.-25° C.  
     
     
         12 . The method of  claim 1  or  2 , further comprising the steps of: 
 providing a die pressing machine comprising: a die with a die hole for forming at least a portion of a cavity, and first and second punches for compacting the powder inside the hole;  
 filling the cavity with the powder with at least an upper end of the second punch inserted into the die hole;  
 compacting the powder in the die between the first and second punches,  
 thereby forming a green compact of the powder; and  
 ejecting the compact out of the die hole.  
 
     
     
         13 . The method of  claim 12 , further comprising the step of sintering the compact.  
     
     
         14 . The method of  claim 13 , wherein said pressing step is performed in a first chamber, and said sintering step is performed in a second chamber having a temperature within 5° C. of the first chamber.