Recycling of tungsten carbides

Abstract

The invention relates to a process for producing an iron- and/or tungsten containing powder or powder agglomerate including the steps of: a) mixing at least a first powder fraction comprising a tungsten carbide containing powder, and at least a second powder fraction comprising an iron oxide powder and/or a tungsten oxide containing powder and optionally an iron powder, the weight of the first fraction being in the range of 50-90% by weight of the mix and the weight of the second fraction being in the range of 10-50% by weight of the mix, b) heating the mix of step a) to a temperature in the range of 400-1300° C., preferably 1000-1200° C. The invention also relates to an iron- and/or tungsten containing powder or powder agglomerate.

1 - 22 . (canceled) 
     
     
         23 . A powder agglomerate formed from a first powder fraction comprising a tungsten carbide containing powder and a second powder fraction comprising an iron oxide powder and/or a tungsten oxide containing powder, the powder agglomerate being suitable for alloying with steel and comprising by weight-% based on the total weight of the powder agglomerate:
 50-99 W;   0-50 Fe;   0-10 Co;   <10 O;   <1 C; and   
       incidental impurities, wherein the powder agglomerate is in the form of pieces of loosely sintered particles, and wherein at least 80% by weight of the pieces have an average diameter greater than 5 mm and a density below 12 g/cm 3 . 
     
     
         24 . The powder agglomerate according to  claim 23 , wherein the powder agglomerate has been produced by a process including the steps of:
 a) mixing the first powder fraction comprising a tungsten carbide containing powder, and the second powder fraction comprising an iron oxide powder and/or a tungsten oxide containing powder, the weight of the first fraction being in the range of 50-90% by weight of the mix and the weight of the second fraction being in the range of 10-50% by weight of the mix; and   b) heating the mix derived from step a) to a temperature in the range of 400-1300° C.   
     
     
         25 . The powder agglomerate according to  claim 23 , wherein at least 80% by weight of the pieces have density below 10 g/cm 3 . 
     
     
         26 . The powder agglomerate according to  claim 23 , wherein at least 80% by weight of the pieces have density in a range of 6 to 9 g/cm 3 . 
     
     
         27 . The powder agglomerate according to  claim 23 , wherein at least 80% by weight of the pieces have an average diameter in the range of 5-100 mm. 
     
     
         28 . The powder agglomerate according to  claim 23 , wherein at least 80% by weight of the pieces have an average diameter in the range of 10-100 mm. 
     
     
         29 . The powder agglomerate according to  claim 23 , wherein at least 80% by weight of the pieces have an average diameter in the range of 20-100 mm. 
     
     
         30 . The powder agglomerate according to  claim 23 , wherein at least 80% by weight of the pieces have an average diameter in the range of 20-40 mm. 
     
     
         31 . The powder agglomerate according to  claim 23 , wherein the powder agglomerate comprises less than 1% by weight of Co. 
     
     
         32 . The powder agglomerate according to  claim 23 , wherein the powder agglomerate comprises less than 0.5% by weight of Co. 
     
     
         33 . The powder agglomerate according to  claim 23 , wherein the powder agglomerate comprises less than 0.2% by weight of Co. 
     
     
         34 . The powder agglomerate according to  claim 23 , wherein the powder agglomerate comprises 1 to 10% by weight of Co. 
     
     
         35 . The powder agglomerate according to  claim 23 , wherein the powder agglomerate comprises 3 to 8% by weight of Co. 
     
     
         36 . The powder agglomerate according to  claim 23 , wherein the powder agglomerate comprises:
 60.1-95 W;   <10 O;   <1 C; and   
       balance Fe and incidental impurities. 
     
     
         37 . The powder agglomerate according to  claim 23 , wherein the powder agglomerate comprising:
 50-95 W;   <10 O;   <1 C;   1-10 wt % Co; and   
       balance Fe and incidental impurities. 
     
     
         38 . The powder agglomerate according to  23 , wherein the content of W is in the range of 60.1-95 wt %. 
     
     
         39 . The powder agglomerate according to  23 , wherein the content of W is in the range of 70-90 wt %. 
     
     
         40 . The powder agglomerate according to  23 , wherein the content of Fe is at least 5 wt %. 
     
     
         41 . The powder agglomerate according to  23 , essentially void of Fe. 
     
     
         42 . The powder agglomerate according to  23 , wherein the first powder fraction is formed from tungsten carbide scrap. 
     
     
         43 . A method of making an alloy comprising adding the powder agglomerate according to  claim 23  to a steel melt to form an alloy. 
     
     
         44 . A powder agglomerate formed from a first powder fraction comprising a tungsten carbide containing powder and a second powder fraction comprising an iron oxide powder and/or a tungsten oxide containing powder, the powder agglomerate being suitable for alloying with steel and comprising by weight-% based on the total weight of the powder agglomerate:
 65-99 W;   0-50 Fe;   0-10 Co;   <10 O;   <1 C; and incidental impurities, wherein the powder agglomerate is in the form of pieces of loosely sintered particles, and wherein at least 80% by weight of the pieces have an average diameter greater than 5 mm and a density below 9 g/cm 3 .   
     
     
         45 . A powder agglomerate formed from a first powder fraction comprising a tungsten carbide containing powder and a second powder fraction comprising an iron oxide powder and/or a tungsten oxide containing powder, the powder agglomerate being suitable for alloying with steel and comprising by weight-% based on the total weight of the powder agglomerate:
 70-99 W;   5-50 Fe;   0-10 Co;   <10 O;   <1 C; and incidental impurities, wherein the powder agglomerate is in the form of pieces of loosely sintered particles, and wherein at least 80% by weight of the pieces have an average diameter greater than 5 mm and a density below 9 g/cm 3 .