Binder for powder metallurgical compositions

Abstract

A binder for metallurgical powder compositions for powder metallurgy (P/M) applications includes styrene/maleic anhydride copolymers and their derivatives. Addition of such binders has improved resistance to dusting, and has improved flow properties of the compositions, even in high relative humidity environments. The compositions can be compacted either at cold or warm temperatures. A mechanical strength of a sintered product containing the binder-treated mix is similar to that of sintered products without the binder.

1 . A metallurgical powder composition comprising a metal powder and from about 0.01% to about 3% of the weight of the metal powder of one of a styrene/maleic anhydride copolymer binder and a derivative thereof.  
   
   
       2 . The composition of  claim 1  wherein the content of said copolymer is from 0.05 wt. % to about 1.5. wt. %.  
   
   
       3 . The composition of  claim 1  further comprising an alloying element powder in the amount of up to about 15 wt. % of the composition.  
   
   
       4 . The composition of  claim 3  wherein said alloying element is one or more selected from the group consisting of elemental copper, nickel, molybdenum, manganese, phosphorus, metallurgical carbon and alloys of the above, with or without iron.  
   
   
       5 . The composition of claim  0 . 1  further comprising a lubricant.  
   
   
       6 . The composition of  claim 1  further comprising a second binder.  
   
   
       7 . The composition of  claim 6  wherein the second binder is selected to chemically interact with the styrene/maleic anhydride copolymer binder to produce an association product, by strong intermolecular acid-base interactions.  
   
   
       8 . The composition of  claim 1  wherein said copolymer is a partially esterified styrene/maleic anhydride copolymer.  
   
   
       9 . The composition of  claim 1  wherein said copolymer is a styrene/maleimide copolymer.  
   
   
       10 . The composition of  claim 1  wherein said copolymer has a weight-average molecular weight between 1,000 and 30,000.  
   
   
       11 . The composition of  claim 8  wherein said copolymer has a weight-average molecular weight between 5,000 and 10,000.  
   
   
       12 . The composition of  claim 1  wherein said copolymer has a glass transition temperature between 30 and 200° C.  
   
   
       13 . The composition of  claim 1  wherein said copolymer has styrene/maleic anhydride ratios between 1:1 and 8:1.  
   
   
       14 . The composition according to  claim 1  wherein said ferrous powder has a maximum particle size less than about 600 microns.  
   
   
       15 . The composition according to  claim 1  adapted to be compacted at temperatures below 200° C. in a die to form parts that are subsequently heat treated at temperatures below 500° C. and/or sintered according to standard powder metallurgy techniques.  
   
   
       16 . A use of styrene/maleic anhydride copolymer and/or a derivative thereof, as a binder for binding a metallurgical powder mixture to form a compactable metal powder composition.  
   
   
       17 . The use according to  claim 16  wherein from about 0.01 wt. % to about 3 wt. % of the styrene/maleic anhydride copolymer or derivative is added to the metallurgical powder mixture.  
   
   
       18 . A method of producing a compactable metal powder composition, the method comprising: 
 providing a metallurgical powder mixture; and    adding from about 0.01 wt. % to about 3 wt. % of a styrene/maleic anhydride copolymer and/or a derivative thereof to the metallurgical powder mixture, to produce a compactable metal powder composition.    
   
   
       19 . A product of the method of  claim 18 .  
   
   
       20 . A method of producing a green piece, the method comprising: 
 placing a compactable metal powder composition according to  claim 1  in a die;    pressing the compactable metal powder composition to form a green piece.    
   
   
       21 . The method according to  claim 20  wherein pressing is applied at a temperature below 200 degrees Celsius.  
   
   
       22 . The method according to  claim 20  further comprising curing the green piece at a temperature below 500 degrees Celsius.  
   
   
       23 . A product of the method of  claim 20 .  
   
   
       24 . A product of the method of  claim 22 .  
   
   
       25 . A method of producing a metal piece, the method comprising sintering the green piece according to  claim 20 .  
   
   
       26 . A method of producing a metal piece, the method comprising sintering the green piece according to  claim 22 .  
   
   
       27 . A kit comprising: 
 a styrene/maleic anhydride copolymer or a derivative thereof having a molecular weight between about 1,000 and 30,000;    a metallurgical powder composition; and    instructions for carrying out the method of  claim 17.