Low expansion corrosion resistant ceramic foam filters for molten aluminum filtration

Abstract

A ceramic foam filter for molten aluminum alloys comprising an alumina silicate rich core and a boron glass shell and a chemical composition comprising: 20-70 wt % Al 2 O 3 , 20-60 wt % SiO 2 , 0-10 wt % CaO, 0-10 wt %; MgO and 2-20 wt % B 2 O 3 .

1 - 34 . (canceled) 
     
     
         35 . A process for forming a ceramic foam filter comprising:
 forming a slurry comprising a solid phase comprising 20-70 wt % alumina, 20-60 wt % silica, 0-20 wt % calcium compound, 0-20 wt % magnesium and 2-20 wt % boron compound and a carrier;   impregnating an open cell foam with said slurry;   volatilizing said carrier; and   heating to form a ceramic foam filter.   
     
     
         36 . The process for forming a ceramic foam filter of  claim 35  wherein said slurry comprises an alumina silicate. 
     
     
         37 . The process for forming a ceramic foam filter of  claim 36  wherein said alumina silicate comprises at least one material selected from the group consisting of mullite, kyanite, silimanite, calcined kaolin and andalusite. 
     
     
         38 . The process for forming a ceramic foam filter of  claim 37  wherein said alumina silicate comprises kyanite. 
     
     
         39 . The process for forming a ceramic foam filter of  claim 37  wherein said alumina silicate consist essentially of kyanite. 
     
     
         40 . The process for forming a ceramic foam filter of  claim 35  wherein said boron compound comprises a compound selected from the group consisting of boric acid, boric oxide, colemanite, calcium borate and a boron glass. 
     
     
         41 . The process for forming a ceramic foam filter of  claim 40  wherein said boron compound is boric acid. 
     
     
         42 - 71 . (canceled)