Patent Publication Number: US-8991611-B2

Title: Separating a powder mixture

Description:
BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to separating components of a powder mixture and, in particular, to methods for using magnets to separating non-magnetic metal particles within a powder mixture. 
     Various industrial parts, such as engine parts are made by pressing a powder material into a die. The quality, strength, etc. of the industrial part is therefore related to the quality of the powder used to make it. Methods of preparing this powder may result in contaminant particles being deposited along with the industrial-use powder material in a powder mixture. Methods have been designed for removing the contaminants from the resulting power mixture by magnetic separation of the particles. However, current magnetic separation methods are ineffective when the powder meant for industrial use and contaminants in the powder mixture are non-magnetic. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one aspect of the invention, a method of separating a powder mixture includes: applying a first magnetic field to the powder mixture containing a non-magnetic metal powder and a contaminant powder, wherein a field strength of the first magnetic field magnetizes the non-magnetic metal powder and leaves the contaminant powder non-magnetized; and applying a second magnetic field to the powder mixture to separate the magnetized metal powder from the non-magnetized contaminant powder. 
     According to another aspect of the invention, an apparatus for separating a powder mixture includes: a first magnet configured to magnetize a non-magnetic metal powder of the powder mixture and leave a contaminant powder of the powder mixture non-magnetized; and a second magnet configured to separate the magnetized metal powder from the non-magnetized contaminant powder. 
     According to yet another aspect of the invention, a method of separating a powder mixture includes: applying an external magnetic field to the powder mixture having a first non-magnetic powder component and a second non-magnetic powder component to magnetize the first non-magnetic component of the powder mixture and leave the second component non-magnetized; and using a second external magnetic field to separate the powder mixture into a first powder and a second powder 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  shows an exemplary system for separation of a powder mixture in one embodiment of the present disclosure; 
         FIG. 2  illustrates an exemplary process for testing a quality of the powder mixture; 
         FIG. 3  shows an alternate embodiment of a separation system of the present disclosure; and 
         FIG. 4  shows a flowchart illustrating an exemplary method of separating a powder mixture. 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an exemplary system  100  for separation of a powder mixture  106  in one embodiment of the present disclosure. The powder mixture  106  may include a mixture of a first powder  106   a  of inherently non-magnetic particles that are to be used in forming an industrial part and a second powder  106   b  including contaminant particles. The inherently non-magnetic particles of the first powder  106   a  may be a metal powder that is non-magnetic but that may be magnetized when subjected to a magnetic field of sufficient field strength. Exemplary non-magnetic metal powders may include, but are not limited to, superalloy metal powder such as high-alloy nickel chromium powder, non-magnetic steel powder, stainless steel powder, and a non-ferrous powder such as a copper powder. For discussion purposes, the non-magnetic metal powder may be referred to herein as a non-magnetic superalloy particle. The contaminant particles of the second powder  106   b  may include particulate forms of material used in a process that produces the first powder that are leftover in the powder mixture  106 . The contaminant material of the second powder  106   b  may include brick flakes, etc. The first powder  106   a  may include particles that, although non-magnetic, may be magnetized when exposed to a magnetic field having a selected field strength, such as a superalloy metal powder. The first powder  106   a  may include non-magnetic particles that remain non-magnetic when exposed to the same magnetic having the selected field strength. 
     The exemplary separation system  100  may include a first magnet  102  for magnetizing the first powder  106   a  (i.e. the superalloy metal powder) of the powder mixture  106  and a second magnet  104  for separating the particles of the first powder  106   a  from particles of the second powder  106   b . In one embodiment, the powder mixture  106  is conveyed through a first magnetic field provided by the first magnet  102  to magnetize the first powder  106   a . Powder mixture  108  therefore contains a magnetized first powder (i.e., magnetized particles of superalloy metal) and non-magnetized second powder (i.e. non-magnetized contaminant particles). In various embodiments, the first magnet  102  may produce a magnetic field having a field strength capable of inducing a magnetic charge on the particles of the first powder  106   a  while the field strength is not enough to induce a magnetic charge on the particles of the second powder  106   b . In various embodiments, the strength of the magnetic field of the first magnet  102  is about 1.5 Tesla or higher. In various embodiments, the magnetic field of the first magnet  102  may be applied at or below room temperatures, i.e, at or below about 25° Celsius. 
     The second magnet  104  is used to separate the magnetized first powder  106   a  of the powder mixture  108  from the second powder  106   b  of the powder mixture  108 . Powder mixture  108  is sent through the magnetic field provided by the second magnet  104 . The second magnet  104  may have a magnetic field strength that is less than the magnetic field strength of the first magnet  102  and that is generally less than a field strength needed to magnetize the particles of the first powder  106   a  and of the second powder  106   b . In one embodiment, the second magnet  104  may be used to produce a magnetic field on a rotating wheel  120  rotating about a horizontal axis. The powder mixture  108  may be introduced to the rotating wheel  120  at the top of the rotating wheel  120 . The magnetized particles of the first powder  106   a  adhere to the wheel  120 . As the wheel  120  rotates, the particles of the first powder  106   a  and the particles of the second powder  106   b  disengage from the rotating wheel  120  at different angles of rotation. A first bin  110  may be placed at a first location with respect to the wheel  120  to catch the particles of the first powder  106   a  and a second bin  112  may be placed at a second location with respect to the wheel  120  to catch the particles of the second powder  106   b  as they disengage from the wheel  120 . In the exemplary separation system  100 , first bin  110  may contain the superalloy metal powder while second bin  112  may include the contaminant particles. Other magnetic separation methods employing the second magnet  104  may be used to separate powder mixture  106  into first bin  110  containing first particles  106   a  and second bin  112  containing second particles  106   b  in alternate embodiments. 
       FIG. 2  illustrates an exemplary process  200  for testing a quality of the powder mixture  106 . The separated second powder  106   b  (i.e., the contaminant particles) from the second bin  112  may be examined for quality control purposes. The contaminant particles may be observed under a tool  202  such as a microscope and a count may be obtained of a number of the contaminant particles. In one embodiment, a size of the contaminant particles may be determined and a count may be obtained of the number of contaminant particles larger that a selected threshold. In an exemplary embodiment, the original powder mixture  106  may be a standard powder sample size from a production lot, such as a 1 lb. Sample from a 500 lb. production lot. An exemplary cleanliness threshold may therefore be a count of 100 or less particles of great size greater than 80 microns or less in size per 1 lb. sample. Thus, a count of less than 20 particles that are greater than 40 microns per 1 lb. sample indicates a sample that is clean enough for use in a subsequent production process. Any particular cleanliness threshold may be used in various embodiments. When the powder mixture  106  is determined to be clean based on the observation of the contaminant particles, the separated first powder  106   a  (i.e., the superalloy metal particles) may be sent for subsequent industrial part production  204 . 
       FIG. 3  shows an alternate embodiment  300  of a separation system of the present disclosure. In the alternate embodiment, the powder mixture  106  is lowered to a freezing temperature or a cryogenic temperature below 0° Celsius. In various embodiments, lowering the temperature of the powder mixture  106  to freezing or cryogenic temperatures increases the responsiveness of the non-magnetic superalloy metal to being magnetized by the first magnetic field of the first magnet  102 . In one alternate embodiment, cooling unit  302  contains the first magnet  102  within. The powder mixture  106  is set inside the cooling unit  302  and the first magnetic field is applied to the powder mixture  106  when the powder mixture  106  reaches the selected temperature. In another alternate embodiment, the powder mixture  106  is cooled to the selected temperature in cooling unit  304  and is exposed to the first magnet  102  soon upon removing the powder mixture  106  from the cooling unit  304  before the powder mixture  106  substantially returns to a room temperature. 
       FIG. 4  shows a flowchart  400  illustrating an exemplary method of separating a powder mixture in one embodiment of the present disclosure. In Block  402 , a powder mixture is obtained that includes a first powder including non-magnetic particles for use in industrial part production and a second power including contaminant particles. In Block  404 , a first magnetic field is applied to the powder mixture to magnetize the particles of the first powder while leaving the particles of the second powder un-magnetized. In Block  406 , a second magnetic field is applied to the powder mixture obtained in Block  404  to separate the powder mixture into a first bin containing the first powder and a second bin containing the second powder. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.